mlx4_core: Fix location of counter index in QP context struct

Fix the address handle portion of the QP context structure to have the
correct bit location for the counter index field.

Signed-off-by: Eli Cohen <eli@mellanox.co.il>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.co.il>
Signed-off-by: Roland Dreier <roland@purestorage.com>