net/mlx5: Forward SRQ resource events

Allow forwarding of SRQ events to mlx5_core interfaces, e.g. mlx5_ib.
Use mlx5_notifier_register/unregister in srq.c in order to allow seamless
transition of srq.c to infiniband subsystem.

Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>