net/atlantic: exclude MACsec counters from xstats

net/atlantic: exclude MACsec counters from xstats

Currently, driver always return full set of xstats counters, including
MACSEC counters. But this driver also supports AQC100 chips, which
does not have MACSEC feature.
This fix adds checking for MACSEC availability (based on FW capability
bits) and returns xstats without MACSEC counters if MACSEC feature
is not available.

Fixes: 09d4dfa85359 ("net/atlantic: implement MACsec statistics")
Cc: stable@dpdk.org
Signed-off-by: Pavel Belous <pavel.belous@aquantia.com>
Signed-off-by: Igor Russkikh <igor.russkikh@aquantia.com>