drm/amd/display: Refactor avi_info_frame colorimetry determination

drm/amd/display: Refactor avi_info_frame colorimetry determination

Replace the messy two if-else chains here that were
on the same value with a switch on the enum.

Signed-off-by: Joshua Ashton <joshua@froggi.es>
Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Cc: Pekka Paalanen <ppaalanen@gmail.com>
Cc: Sebastian Wick <sebastian.wick@redhat.com>
Cc: Vitaly.Prosyak@amd.com
Cc: Joshua Ashton <joshua@froggi.es>
Cc: Simon Ser <contact@emersion.fr>
Cc: Melissa Wen <mwen@igalia.com>
Cc: dri-devel@lists.freedesktop.org
Cc: amd-gfx@lists.freedesktop.org
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>