drm/amd/display: clean up some header paths

[Why]
Some include paths don't need to have relative paths
And some types missing

[How]
make some changes to headers and modify include path

Signed-off-by: Anthony Koo <Anthony.Koo@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>