RDMA/siw: Fix potential NULL de-ref

In siw_connect() we have an error flow where there is no valid qp
pointer.  Make sure we don't try to de-ref in that situation.

Fixes: 6c52fdc2 ("rdma/siw: connection management")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Bernard Metzler <bmt@zurich.ibm.com>
Link: https://lore.kernel.org/r/20190819140257.19319-1-bmt@zurich.ibm.com


Signed-off-by: Doug Ledford <dledford@redhat.com>