net/ena: fix setting Rx checksum flags in mbuf

net/ena: fix setting Rx checksum flags in mbuf

The driver was never setting PKT_RX_*_CKSUM_GOOD flags, so the only way
of checking if the checksum was checked was by testing for the
PKT_RX_*_CKSUM_BAD. In that situation, the application couldn't detect
if the checksum was valid or unknown, as unknown flag is equal to 0.

Moreover, the l3_csum_err value is only valid if the l3_proto is
indicating IPv4, so it shouldn't be checked for other protocols.

Fixes: 1173fca25af9 ("ena: add polling-mode driver")
Cc: stable@dpdk.org
Signed-off-by: Michal Krawczyk <mk@semihalf.com>
Reviewed-by: Igor Chauskin <igorch@amazon.com>
Reviewed-by: Guy Tzalik <gtzalik@amazon.com>