RDMA/siw: Suppress uninitialized var warning

RDMA/siw: Suppress uninitialized var warning

drivers/infiniband/sw/siw/siw_qp_rx.c: In function siw_proc_send:
./include/linux/spinlock.h:288:3: warning: flags may be used uninitialized in this function [-Wmaybe-uninitialized]
   _raw_spin_unlock_irqrestore(lock, flags); \
   ^~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/infiniband/sw/siw/siw_qp_rx.c:335:16: note: flags was declared here
  unsigned long flags;

Link: https://lore.kernel.org/r/20200323184627.ZWPg91uin%akpm@linux-foundation.org
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>