RDMA/bnxt_re: Wait for all the CQ events before freeing CQ data structures

Destroy CQ command to firmware returns the num_cnq_events as a
response. This indicates the driver about the number of CQ events
generated for this CQ. Driver should wait for all these events before
freeing the CQ host structures.  Also, add routine to clean all the
pending notification for the CQs getting destroyed. This avoids the
possibility of accessing the CQ data structures after its freed.

Fixes: 1ac5a404 ("RDMA/bnxt_re: Add bnxt_re RoCE driver")
Link: https://lore.kernel.org/r/1584120842-3200-1-git-send-email-selvin.xavier@broadcom.com


Signed-off-by: Selvin Xavier <selvin.xavier@broadcom.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>