bridge: vlan: add global mcast_querier_interval option

bridge: vlan: add global mcast_querier_interval option

Add control and dump support for the global mcast_querier_interval
option which controls the interval after which if no other router
queries are seen the bridge will start sending its own queries.
To be consistent with the same bridge-wide option the value is reported
with USER_HZ granularity and the same granularity is expected when
setting it.
Syntax:
 $ bridge vlan global set dev bridge vid 1 mcast_querier_interval 13000

Signed-off-by: Nikolay Aleksandrov <nikolay@nvidia.com>
Signed-off-by: David Ahern <dsahern@kernel.org>