drm/amd/display: Correct color depth for SelectCRTC_Source

drm/amd/display: Correct color depth for SelectCRTC_Source

Pass the correct enum values as expected by the VBIOS.
Previously the actual bit depth integer value was passed,
which was a mistake.

Fixes: 7fb4f254c8eb ("drm/amd/display: Add SelectCRTC_Source to BIOS parser")
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit cdf6e4c0cdab129ffc4e41a8ac53a0738f805072)