macsec: double accounting of dropped rx/tx packets

The macsec implementation shouldn't account for rx/tx packets that are
dropped in the netdev framework. The netdev framework itself accounts
for such packets by atomically updating struct net_device`rx_dropped and
struct net_device`tx_dropped fields. Later on when the stats for macsec
link is retrieved, the packets dropped in netdev framework will be
included in dev_get_stats() after calling macsec.c`macsec_get_stats64()

Signed-off-by: Girish Moodalbail <girish.moodalbail@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>