i40iw: Add NULL check for ibqp event handler

Add NULL check for ibqp event handler before calling it to report
QP events, as it might not initialized.

Signed-off-by: Shiraz Saleem <shiraz.saleem@intel.com>
Signed-off-by: Faisal Latif <faisal.latif@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>