net: ena: add good checksum counter

Add a new statistics to ETHTOOL to specify if the device calculated
and validated the Rx csum.

Signed-off-by: Evgeny Shmeilin <evgeny@annapurnaLabs.com>
Signed-off-by: Sameeh Jubran <sameehj@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>