nfp: flower: fix multiple keys per pedit action

Previously we only allowed a single header key per pedit action to
change the header. This used to result in the last header key in the
pedit action to overwrite previous headers. We now keep track of them
and allow multiple header keys per pedit action.

Fixes: c0b1bd9a ("nfp: add set ipv4 header action flower offload")
Fixes: 354b82bb ("nfp: add set ipv6 source and destination address")
Fixes: f8b7b0a6 ("nfp: add set tcp and udp header action flower offload")
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>