ionic: protect vf calls from fw reset

When going into a firmware upgrade cycle, we set the device as
not present to keep some user commands from trying to change
the driver while we're only half there.  Unfortunately, the
ndo_vf_* calls don't check netif_device_present() so we need
to add a check in the callbacks.

Signed-off-by: Shannon Nelson <snelson@pensando.io>
Signed-off-by: David S. Miller <davem@davemloft.net>