kernel-interface: Remove reqid parameter from get_spi/get_cpi() methods

kernel-interface: Remove reqid parameter from get_spi/get_cpi() methods

The reqid is not strictly required, as we set the reqid with the update
call when installing the negotiated SA.

If we don't need a reqid at this stage, we can later allocate the reqid in
the kernel backend once the SA parameters have been fully negotaited. This
allows us to assign the same reqid for the same selectors to avoid conflicts
on backends this is necessary.