net/mlx4_core: Fix wrong mask applied on EQ numbers in the wrapper

Currently the  mask is wrongly set in the MAP_EQ wrapper, fix that.
Without the fix any EQ number above 511 is mapped to one below 511.

Signed-off-by: Moshe Lazer <moshel@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>