mlx4: Fix wrong endianess access with QP context flags

We wrongly tested QP context bits without BE conversion
as was spotted by sparse...

drivers/infiniband/hw/mlx4/qp.c:1685:38: sparse: restricted __be32 degrades to integer

Fix that!

Fixes: d2fce8a9

 ('mlx4: Set user-space raw Ethernet QPs to properly handle VXLAN traffic')
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>