drm/amd/display: convert link.h functions to function pointer style

[Why & How]
All dc subcomponents should call another dc component via function pointers
stored in a component structure. This is part of dc coding convention since
the beginning. The reason behind this is to improve encapsulation and
polymorphism. The function contract is extracted into a single link service
structure defined in link.h header file and implemented only in link_factory.c instead
of spreading across multiple files in link component file structure.

Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Wenjing Liu <wenjing.liu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drm/amd/display: move dc_link functions in protocols folder to dc_link_exports

[why]
link component should only have one interface serving dc.

[how]
We are moving dc_link functions exposed to DM to dc_link_exports
and unify link component interface in link.h with function pointer
to match the style of other dc component. This is the third step to move
dc_link functions under protocols folder to dc_link_exports.

Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Wenjing Liu <wenjing.liu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drm/amd/display: move dc_link functions in accessories folder to dc_link_exports

[why]
link component should only have one interface serving dc.

[how]
We are moving dc_link functions exposed to DM to dc_link_exports
and unify link component interface in link.h with function pointer
to match the style of other dc component. This is the first step to move
dc_link functions under accessories folder to dc_link_exports.

Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Wenjing Liu <wenjing.liu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drm/amd/display: do not set RX back to SST mode for non 0 mst stream count

[why]
a recent regression has caused us to mistakenly switch RX back to SST mode
when there are remaining mst stream enabled to the link. We are missing
a condition check for stream count before setting RX back to SST mode.

[how]
Add stream count check condition back and do some further refactor so the
logic is easier to understand to prevent future coding error in this sequence.

Reviewed-by: Samson Tam <Samson.Tam@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Wenjing Liu <wenjing.liu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drm/amd/display: break down dc_link.c

[why]
dc_link contains over 30k line of code, the decision is to break it
down to files residing in link folder based on functionality. This
change is the last break down change which will remove dc_link.c
file after everything is broken down.

[how]
Move remaining dc_link.c functions into link_detection, link_dpms,
link_validation, link_resource, and link_fpga and remove dc_link.

Reviewed-by: George Shen <George.Shen@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Wenjing Liu <wenjing.liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drm/amd/display: create accessories, hwss and protocols sub folders in link

[why]
link component contains three sub folders:

accessories - utilities for improving testability, logging or tracing, doesn't impact
end user use cases.

protocols - specs defined protocols used in end user use cases

hwss - hwss owned link_hwss object, served as an abstraction layer in hwss to
access various types of encoder/phy/dpia endpoints in a unified interface.

sooner we will have files directly under link folder one for the implementation of
each major link behavior such as link_create, link_detect, link_validate
and link_set_dpms.

Reviewed-by: George Shen <George.Shen@amd.com>
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Alan Liu <HaoPing.Liu@amd.com>
Signed-off-by: Wenjing Liu <wenjing.liu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>