drm/amd/pm: relocate the power related headers

Instead of centralizing all headers in the same folder. Separate them into
different folders and place them among those source files those who really
need them.

Signed-off-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drm/amd/pm: create a new holder for those APIs used only by legacy ASICs(si/kv)

Those APIs are used only by legacy ASICs(si/kv). They cannot be
shared by other ASICs. So, we create a new holder for them.

Signed-off-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drm/amd/pm: optimize the power related source code layout

The target is to provide a clear entry point(for power routines).
Also this can help to maintain a clear view about the frameworks
used on different ASICs. Hopefully all these can make power part
more friendly to play with.

Signed-off-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>