We accidentally forgot to set the error code if ib_copy_from_udata()
fails.  It means we return ERR_PTR(0) which is NULL and results in a
NULL dereference in the callers.

Fixes: d3749841 ("i40iw: add files for iwarp interface")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Shiraz Saleem <shiraz.saleem@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>