Fix a limit condition of vlans on the interface before setting vlan
promiscuous mode

Fixes: 48dd73d0 ("net: aquantia: fix vlans not working over bridged network")
Signed-off-by: Dmitry Bogdanov <dmitry.bogdanov@aquantia.com>
Signed-off-by: Igor Russkikh <igor.russkikh@aquantia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>