drm/amd/display: Add basic ODM description

Add kernel-doc to some of the ODM-related functions.

Tested-by: Mark Broadworth <mark.broadworth@amd.com>
Reviewed-by: Aurabindo Pillai <Aurabindo.Pillai@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>