RDMA/uverbs: Track dmabuf memory regions

The dmabuf memory registrations are missing the restrack handling and
hence do not appear in rdma tool.

Fixes: bfe0cc6eb249 ("RDMA/uverbs: Add uverbs command for dma-buf based MR registration")
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Gal Pressman <[e-mail]>
Reviewed-by: Leon Romanovsky <[e-mail]>
Signed-off-by: Jason Gunthorpe <[e-mail]>

drivers/infiniband/core/uverbs_std_types_mr.c

···
 	mr->uobject = uobj;
 	atomic_inc(&pd->usecnt);
 
+	rdma_restrack_new(&mr->res, RDMA_RESTRACK_MR);
+	rdma_restrack_set_name(&mr->res, NULL);
+	rdma_restrack_add(&mr->res);
 	uobj->object = mr;
 
 	uverbs_finalize_uobj_create(attrs, UVERBS_ATTR_REG_DMABUF_MR_HANDLE);