net_sched: flower: Add vlan support

Enhance flower to support 802.1Q vlan protocol classification.
Currently, the supported fields are vlan_id and vlan_priority.

Example:

	# add a flower filter with vlan id and priority classification
	tc filter add dev ens4f0 protocol 802.1Q parent ffff: \
		flower \
		indev ens4f0 \
		vlan_ethtype ipv4 \
		vlan_id 100 \
		vlan_prio 3 \
	action vlan pop

Signed-off-by: Hadar Hen Zion <hadarh@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>