drm/amd/display: Enable EASF based on luma taps only

drm/amd/display: Enable EASF based on luma taps only

[WHY]
EASF only applies to luma. Previously both luma and chroma taps
were checked to determine whether to enable EASF.

[HOW]
Only check if luma taps are supported before determining whether
to enable EASF or not.

Reviewed-by: Alvin Lee <alvin.lee2@amd.com>
Signed-off-by: Samson Tam <Samson.Tam@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>