net/i40e: support power management on VF

net/i40e: support power management on VF

When .get_monitor_addr API was introduced, it was implemented in the
i40e driver, but only for the physical function; the virtual function
portion of the driver does not support that API.

Add the missing function pointer to VF device structure.

The i40e driver is not meant to use the VF portion any more, as
currently i40e VF devices are supposed to be managed by iavf drier, but
add this just in case it needs backporting later.

Fixes: a683abf90a22 ("net/i40e: implement power management API")
Cc: stable@dpdk.org
Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
Reviewed-by: David Hunt <david.hunt@intel.com>