nfp: add a separate counter for packets with CHECKSUM_COMPLETE

We are currently counting packets with CHECKSUM_COMPLETE as
"hw_rx_csum_ok".  This is confusing.  Add a new counter.
To make sure it fits in the same cacheline move the less used
error counter to a different location.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Dirk van der Merwe <dirk.vandermerwe@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>