drm/amd/display: Simplify register offsets

[Why]
Runtime initialization of register addresses define
duplicate register offsets in resource file, and makes
register offsets in sub-block defined for compile
time initialization obsolete.

[How]
Remove obsolete sub block register offsets that is
no longer referenced.

Reviewed-by: Martin Leung <Martin.Leung@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Chris Park <chris.park@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>