RDMA/bnxt_re: Fix static checker warning

If there is ever any error while creating srq->umem, we return that
error, we don't store it in srq->umem, so any check of srq->umem for
IS_ERR is pointless.  Further, checking udata is unnecessary as
srq->umem is always either NULL or valid, without respect to udata.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>