lib/tc: treat vlan id and prio as independent fields

lib/tc: treat vlan id and prio as independent fields

Previously the key was used to check the presence of vlan id and
prio fields instead of using the mask. Additionally the vlan id
field was considered to be present if only the prio field was set,
and vice versa. f.e. setting the following:

ovs-ofctl -OOpenFlow13,OpenFlow15 add-flow br0 \
priority=10,cookie=1,table=0,ip,dl_vlan_pcp=2,actions=output:2

Resulted in (instead of wildcarding vlan_id, filter matches 0):
filter protocol 802.1Q pref 1 flower chain 0
filter protocol 802.1Q pref 1 flower chain 0 handle 0x1
 vlan_id 0
 vlan_prio 2
 vlan_ethtype ip
 eth_type ipv4
 ip_flags nofrag
 in_hw
       action order 1: mirred (Egress Redirect to device eth1) stolen
       index 2 ref 1 bind 1 installed 5 sec used 5 sec
       Action statistics:
       Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
       backlog 0b 0p requeues 0
       cookie 47040ae7a94fff6afd7ed8aa04b11ba4

Signed-off-by: Pieter Jansen van Vuuren <pieter.jansenvanvuuren@netronome.com>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: Simon Horman <simon.horman@netronome.com>