Do not dereference 'siw_crypto_shash' before checking

Reported-by: "Dan Carpenter" <dan.carpenter@oracle.com>
Fixes: f29dd55b ("rdma/siw: queue pair methods")
Link: https://lore.kernel.org/r/OF61E386ED.49A73798-ON00258444.003BD6A6-00258444.003CC8D9@notes.na.collabserv.com


Signed-off-by: Bernard Metzler <bmt@zurich.ibm.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>