IB/mlx4: Fix potential deadlock when sending mad to wire

send_mad_to_wire takes the same spinlock that is taken in
the interrupt context.  Therefore, it needs irqsave/restore.

Fixes: b9c5d6a6 ('IB/mlx4: Add multicast group (MCG) paravirtualization for SR-IOV')
Signed-off-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>