drm/amd/display: Fix comments

[Why & how]
Fix format and typo of comments.

Acked-by: Alan Liu <HaoPing.Liu@amd.com>
Signed-off-by: Samson Tam <Samson.Tam@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>