i40iw: Refactor of driver generated AEs

The flush CQP OP can be used to optionally generate
Asynchronous Events (AEs) in addition to QP flush.
Consolidate all HW AE generation code under a new
function i40iw_gen_ae which use the flush CQP OP
to only generate AEs.

Signed-off-by: Henry Orosco <henry.orosco@intel.com>
Signed-off-by: Shiraz Saleem <shiraz.saleem@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>