nfp: flower: fix vlan match by checking both vlan id and vlan pcp

Previously we only checked if the vlan id field is present when trying
to match a vlan tag. The vlan id and vlan pcp field should be treated
independently.

Fixes: 5571e8c9 ("nfp: extend flower matching capabilities")
Signed-off-by: Pieter Jansen van Vuuren <pieter.jansenvanvuuren@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>