net: lan966x: Fix potential null-ptr-deref in lan966x_stats_init()

lan966x_stats_init() calls create_singlethread_workqueue() and not
checked the ret value, which may return NULL. And a null-ptr-deref may
happen:

lan966x_stats_init()
create_singlethread_workqueue() # failed, lan966x->stats_queue is NULL
queue_delayed_work()
queue_delayed_work_on()
__queue_delayed_work() # warning here, but continue
__queue_work() # access wq->flags, null-ptr-deref

Check the ret value and return -ENOMEM if it is NULL.

Fixes: 12c2d0a5b8e2 ("net: lan966x: add ethtool configuration and statistics")
Signed-off-by: Shang XiaoJing <shangxiaojing@huawei.com>
Reviewed-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: lan966x: Fix the rx drop counter

Currently the rx drop is calculated as the sum of multiple HW drop
counters. The issue is that not all the HW drop counters were added for
the rx drop counter. So if for example you have a police that drops
frames, they were not see in the rx drop counter.
Fix this by updating how the rx drop counter is calculated. It is
required to add also RX_RED_PRIO_* HW counters.

Fixes: 12c2d0a5b8e2 ("net: lan966x: add ethtool configuration and statistics")
Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Link: https://lore.kernel.org/r/20221019083056.2744282-1-horatiu.vultur@microchip.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net: lan966x: Implement get_ts_info

Implement the function get_ts_info in ethtool_ops which is needed to get
the HW capabilities for timestamping.

Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: lan966x: add ethtool configuration and statistics

This patch adds support for statistics counters for the network
interfaces. Also adds support for configuring the network interface via
ethtool like: speed, duplex etc.

Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>