net: bridge: fix undefined br_vlan_can_enter_range in tunnel code

If bridge vlan filtering is not defined we won't have
br_vlan_can_enter_range and thus will get a compile error as was
reported by Stephen and the build bot. So let's define a stub for when
vlan filtering is not used.

Fixes: 94339443 ("net: bridge: notify on vlan tunnel changes done via the old api")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>