drm/radeon: handle NULL bo->resource in move callback

The ttm bo now initially has NULL bo->resource, and leaves the driver
the handle that. However it looks like we forgot to handle that for
radeon.  It looks like this will just null-ptr-deref in
radeon_bo_move(), if bo->resource is NULL.

Fix this by calling move_null().

Fixes: 18025378 ("drm/ttm: stop allocating dummy resources during BO creation")
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230208145319.397235-4-matthew.auld@intel.com


Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Christian König <christian.koenig@amd.com>