i40iw: Clear CQP Head/Tail during initialization

Clear Control Queue Pair (CQP) Head/Tail on CQP
initialization as during an adapter reset, these
values are not reinitialized. Tail is cleared by
writing 0 to CQP's tail register. Head is cleared
by writing 0 to CQP's doorbell register.

Fixes: 86dbcd0f ("i40iw: add file to handle cqp calls")
Signed-off-by: Christopher Bednarz <christopher.n.bednarz@intel.com>
Signed-off-by: Shiraz Saleem <shiraz.saleem@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>