i40iw: Remove unused structures

Some structures for post SQ operation are not used.
Remove the following:

i40iw_post_send_w_inv
i40iw_post_inline_send_w_inv
send_w_sol
send_w_inv
send_w_sol_inv
inline_send_w_sol
inline_send_w_inv
inline_send_w_sol_inv

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>