drm/amd/display: Rework comments on dc file

The file dc.c has multiple comments that do not follow the kernel-doc or
are made in a distracting way. This commit alleviates part of this issue
by reorganizing some comments inside the dc file.

Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Reviewed-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>