drm/amd/display: Remove nv12 work around

[Why]
dal side nv12 wa has a lot of side effects.
KMD side wa is used, so this should be remove.

[How]
Removed wa from dal side.

Signed-off-by: Yongqiang Sun <yongqiang.sun@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>