net: aquantia: Extend stat counters to 64bit values

Device hardware provides only 32bit counters. Using these directly
causes byte counters to overflow soon. A separate nic level structure
with 64 bit counters is now used to collect incrementally all the stats
and report these counters to ethtool stats and ndev stats.

Signed-off-by: Igor Russkikh <igor.russkikh@aquantia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>