drm/amd/display: allow chroma 1:1 scaling when sharpness is off

[Why]
SPL code forces taps to 1 when ratio is 1:1 and sharpness is off
But for chroma 1:1, need taps > 1 to handle cositing

[How]
Do not force chroma taps to 1 when ratio is 1:1 for YUV420
Remove 420_CHROMA_BYPASS mode for scaler

Reviewed-by: Navid Assadian <navid.assadian@amd.com>
Signed-off-by: Samson Tam <Samson.Tam@amd.com>
Signed-off-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>