drm/amdgpu: cleanup on error in amdgpu_cs_ioctl()

We recently changed the locking in this function and now there is a
missing unlock on error.  Also there are some other resources that we
should probably release as well...

Fixes: f48b2659 ('drm/amdgpu: fix the broken vm->mutex V2')
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>