net sched: update vlan action for batched events operations

Add get_fill_size() routine used to calculate the action size
when building a batch of events.

Fixes: c7e2b968

 ("sched: introduce vlan action")
Signed-off-by: Roman Mashak <mrv@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>