net/mlx5e: Get the latest values from counters in switchdev mode

commit dcdf4ce0 upstream.

In the switchdev mode, when running "cat
/sys/class/net/NIC/statistics/tx_packets", the ppcnt register is
accessed to get the latest values. But currently this command can
not get the correct values from ppcnt.

From firmware manual, before getting the 802_3 counters, the 802_3
data layout should be set to the ppcnt register.

When the command "cat /sys/class/net/NIC/statistics/tx_packets" is
run, before updating 802_3 data layout with ppcnt register, the
monitor counters are tested. The test result will decide the
802_3 data layout is updated or not.

Actually the monitor counters do not support to monitor rx/tx
stats of 802_3 in switchdev mode. So the rx/tx counters change
will not trigger monitor counters. So the 802_3 data layout will
not be updated in ppcnt register. Finally this command can not get
the latest values from ppcnt register with 802_3 data layout.

Fixes: 5c7e8bbb ("net/mlx5e: Use monitor counters for update stats")
Signed-off-by: Zhu Yanjun <yanjunz@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>