drm/amd/display: Trivial code style adjustment

Just adjust the code indentation in the header and add a simple comment
in the dm_cp_psp file.

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