Revert "drm/amdgpu: Ensure that the modifier requested is supported by plane."

Revert "drm/amdgpu: Ensure that the modifier requested is supported by plane."

This reverts commit f4a9be998c8ee39a30a68cb775c91928fe10a384.

The original commit was found to cause the following two issues
on sienna cichlid:
1. Refresh rate locked during vrrdemo
2. Display sticks on flipped landscape mode after changing
   orientation, and cannot be changed back to regular landscape

Signed-off-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>