i40iw: Add missing memory barriers

Remove duplicate set_64bit_val call to offset 24.
Replace some instances of set_64bit_val with
i40iw_insert_wqe_hdr as valid bit needs a write
barrier and should be the last write operation for the WQE.

Fixes: 786c6adb

 ("i40iw: add puda code")
Signed-off-by: Mustafa Ismail <mustafa.ismail@intel.com>
Signed-off-by: Shiraz Saleem <shiraz.saleem@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>