mlx4: fix warning in drivers/net/mlx4/mcg.c

fix warning:

  drivers/net/mlx4/mcg.c: In function ‘mlx4_multicast_attach’:
  drivers/net/mlx4/mcg.c:217: warning: integer overflow in expression

there was no real danger of overflow here though.

md5:
   db8eb55620f886c03854a2abb2ce6c3f  mcg.o.before.asm
   db8eb55620f886c03854a2abb2ce6c3f  mcg.o.after.asm
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/mlx4/mcg.c

@@ -205,7 +205,7 @@ int mlx4_multicast_attach(struct mlx4_dev *dev, struct mlx4_qp *qp, u8 gid[16],
 
 	if (block_mcast_loopback)
 		mgm->qp[members_count++] = cpu_to_be32((qp->qpn & MGM_QPN_MASK) |
-						       (1 << MGM_BLCK_LB_BIT));
+						       (1U << MGM_BLCK_LB_BIT));
 	else
 		mgm->qp[members_count++] = cpu_to_be32(qp->qpn & MGM_QPN_MASK);