net/ena: advertise scattered Rx capability

net/ena: advertise scattered Rx capability

ENA can't be forced to always pass single descriptor for the Rx packet.
Even if the passed buffer size is big enough to hold the data, we can't
make assumption that the HW won't use extra descriptor because of
internal optimizations. This assumption may be true, but only for some
of the FW revisions, which may differ depending on the used AWS instance
type.

As the scattered Rx support on the Rx path already exists, the driver
just needs to announce DEV_RX_OFFLOAD_SCATTER capability by turning on
the rte_eth_dev_data::scattered_rx option.

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: Shai Brandes <shaibran@amazon.com>