net: make dev_disable_lro use physical device if passed a vlan dev (v2)

If the device passed into dev_disable_lro is a vlan, then repoint the dev
poniter so that we actually modify the underlying physical device.

Signed-of-by: Neil Horman <nhorman@tuxdriver.com>
CC: davem@davemloft.net
CC: bhutchings@solarflare.com
Signed-off-by: David S. Miller <davem@davemloft.net>