drm/amd/display: Add hdr_supported flag

Signed-off-by: Yongqiang Sun <yongqiang.sun@amd.com>
Reviewed-by: Anthony Koo <Anthony.Koo@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>