Look at connector->colorimetry to determine output colorspace.

We don't want to impact current SDR behavior, so
DRM_MODE_COLORIMETRY_DEFAULT preserves current behavior.

Also add support to explicitly set BT601 and BT709.

v4:
- Roll support for BT709 and BT601 into this patch
- Add default case to avoid warnings for unhandled
  enum values
Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Joshua Ashton <joshua@froggi.es>

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>