RDMA/srpt: Fix handling of iWARP logins

The path_rec pointer is NULL set for IB and RoCE logins but not for iWARP
logins. Hence check the path_rec pointer before dereferencing it.

Link: https://lore.kernel.org/r/20190930231707.48259-11-bvanassche@acm.org


Cc: Honggang LI <honli@redhat.com>
Cc: Laurence Oberman <loberman@redhat.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>