drm/amdgpu/userq: drop VCN and VPE doorbell handling

drm/amdgpu/userq: drop VCN and VPE doorbell handling

VCN and VPE userqs are not yet supported and this code is
not correct.  Userspace should provide the correct
doorbell offset with in their doorbell page for the IP.
Adjusting it here will not work as expected as userspace
and the queue itself will have different offsets.

We need to add a INFO IOCTL query to get the offset and
range for each IP within the doorbell page to handle this
properly.

Cc: Saleemkhan Jamadar <saleemkhan.jamadar@amd.com>
Reviewed-by: Saleemkhan Jamadar <saleemkhan.jamadar@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>