i40iw: Refactor handling of txpend list

Currently the TX pending lists for IEQ and ILQ are
handled separately. The handling of both can be
consolidated in i40iw_poll_completion.

Signed-off-by: Mustafa Ismail <mustafa.ismail@intel.com>
Signed-off-by: Shiraz Saleem <shiraz.saleem@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>