net/ena: expose ENI stats as additional xstats

net/ena: expose ENI stats as additional xstats

New HAL allows driver to read extra ENI stats. Exact meaning of each of
them can be found in base/ena_defs/ena_admin_defs.h file and structure
ena_admin_eni_stats.

The ena_eni_stats structure is exactly the same as ena_admin_eni_stats,
but it was required to be added for compatibility with xstats macros.

Reading ENI stats requires communication with the admin queue.

Signed-off-by: Michal Krawczyk <mk@semihalf.com>
Reviewed-by: Igor Chauskin <igorch@amazon.com>
Reviewed-by: Guy Tzalik <gtzalik@amazon.com>
Reviewed-by: Stephen Hemminger <stephen@networkplumber.org>