net: atlantic: split rx and tx per-queue stats

This patch splits rx and tx per-queue stats.
This change simplifies the follow-up introduction of PTP stats and
u64_stats_update_* usage.

Signed-off-by: Mark Starovoytov <mstarovoitov@marvell.com>
Signed-off-by: Igor Russkikh <irusskikh@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>