net: atlantic: fix out of range usage of active_vlans array

commit 5a292c89 upstream.

fix static checker warning:
 drivers/net/ethernet/aquantia/atlantic/aq_filters.c:166 aq_check_approve_fvlan()
 error: passing untrusted data to 'test_bit()'

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Fixes: 7975d2af: ("net: aquantia: add support of rx-vlan-filter offload")
Signed-off-by: Dmitry Bogdanov <dbogdanov@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>