drm/amd/display: avoid stringop-overflow warnings for dp_decide_lane_settings()

gcc prints a warning about a possible array overflow for a couple of
callers of dp_decide_lane_settings() after commit 1b56c90018f0 ("Makefile:
Enable -Wstringop-overflow globally"):

drivers/gpu/drm/amd/amdgpu/../display/dc/link/protocols/link_dp_training_fixed_vs_pe_retimer.c: In function 'dp_perform_fixed_vs_pe_training_sequence_legacy':
drivers/gpu/drm/amd/amdgpu/../display/dc/link/protocols/link_dp_training_fixed_vs_pe_retimer.c:426:25: error: 'dp_decide_lane_settings' accessing 4 bytes in a region of size 1 [-Werror=stringop-overflow=]
426 | dp_decide_lane_settings(lt_settings, dpcd_lane_adjust,
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
427 | lt_settings->hw_lane_settings, lt_settings->dpcd_lane_settings);
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/amd/amdgpu/../display/dc/link/protocols/link_dp_training_fixed_vs_pe_retimer.c:426:25: note: referencing argument 4 of type 'union dpcd_training_lane[4]'

I'm not entirely sure what caused this, but changing the prototype to expect
a pointer instead of an array avoids the warnings.

Fixes: 7727e7b60f82 ("drm/amd/display: Improve robustness of FIXED_VS link training at DP1 rates")
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org> # build-tested
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
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 dp irq handler functions from dc_link_dp to link_dp_irq_handler

Create new files link_dp_irq_handler.c and link_dp_irq_handler.h, and
move DP irq handler functions into them.

Reviewed-by: George Shen <George.Shen@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>

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>