RDMA/bnxt_re: synchronize poll_cq and req_notify_cq verbs

Synchronize poll_cq and req_notify_cq verbs using cq_lock,
instead of the lower level qplib->hwq.lock.

Signed-off-by: Selvin Xavier <selvin.xavier@broadcom.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>