f_flower: Add num of vlans parameter

f_flower: Add num of vlans parameter

Our customers in the fiber telecom world have network configurations
where they would like to control their traffic according to the number
of tags appearing in the packet.

For example, TR247 GPON conformance test suite specification mostly
talks about untagged, single, double tagged packets and gives lax
guidelines on the vlan protocol vs. number of vlan tags.

This is different from the common IT networks where 802.1Q and 802.1ad
protocols are usually describe single and double tagged packet. GPON
configurations that we work with have arbitrary mix the above protocols
and number of vlan tags in the packet.

This patch adds num_of_vlans flower key and associated print and parse
routines. The following command becomes possible:

tc filter add dev eth1 ingress flower num_of_vlans 1 action drop

Signed-off-by: Boris Sukholitko <boris.sukholitko@broadcom.com>
Signed-off-by: David Ahern <dsahern@kernel.org>