net/ena: refactor ena_get_stats64 to be atomic context safe

net/ena: refactor ena_get_stats64 to be atomic context safe

Orabug: 25535122

ndo_get_stat64() can be called from atomic context, but the current
implementation sends an admin command to retrieve the statistics from
the device. This admin command can sleep.

This patch re-factors the implementation of ena_get_stats64() to use
the {rx,tx}bytes/count from the driver's inner counters, and to obtain
the rx drop counter from the asynchronous keep alive (heart bit)
event.

Signed-off-by: Netanel Belgazal <netanel@annapurnalabs.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit d81db24056132fe8b83e2fba337e9ea76675e68d)
Signed-off-by: Brian Maly <brian.maly@oracle.com>
Conflicts:
	drivers/net/ethernet/amazon/ena/ena_netdev.c