Revert "drm/amdgpu: move nbio sdma_doorbell_range() into sdma code for vega"

This reverts commit 9f55f36f which is
commit e3163bc8 upstream.

This commit causes repeated WARN_ONs from

drivers/gpu/drm/amd/amdgpu/../display/amdgpu_dm/amd
gpu_dm.c:7391 amdgpu_dm_atomic_commit_tail+0x23b9/0x2430 [amdgpu]

dmesg fills up with the following messages and drm initialization takes
a very long time.

Cc: <stable@vger.kernel.org>    # 5.10
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>