RDMA/iw_cxgb4: Drop __GFP_NOFAIL

There is no reason for this __GFP_NOFAIL, none of the other routines in
this file use it, and there is an error unwind here. NOFAIL should be
reserved for special cases, not used by network drivers.

Fixes: 6a0b6174 ("rdma/cxgb4: Add support for kernel mode SRQ's")
Reported-by: Nicholas Mc Guire <hofrat@osadl.org>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>