RDMA/amso1100: Initialize the wait_queue_head_t in the c2_qp structure

Fix a crash if the driver has to wait for a QP reference to be dropped
when destroying the QP.

Signed-off-by: Ethan Burns <eaburns@iol.unh.edu>
Acked-by: Tom Tucker <tom@opengridcomputing.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>