i40e: lie to the VF

If an untrusted VF attempts to configure promiscuous mode, log a message
pointing out its naughty behavior. But then, instead of returning an
error to the offender, just lie to it and say everything's OK. It will
continue on its way, thinking it's in promiscuous mode, but receiving no
packets except its own.

Change-ID: I63369215b1720f3c531eedfc06af86ff8c0e3dc8
Signed-off-by: Mitch Williams <mitch.a.williams@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>