eth: mlx5: Move pause storm errors to pause stats

eth: mlx5: Move pause storm errors to pause stats

Report device_stall_critical_watermark_cnt as tx_pause_storm_events in
the ethtool_pause_stats struct. This counter tracks pause storm error
events which indicate the NIC has been sending pause frames for an
extended period due to a stall.

The ethtool_pause_stats struct reports these stalls as a single value,
whereas the device supports tracking them per priority. Aggregate the
counter across all priority classes to capture stalls on all priorities.
Note that the stats are fetched from the device for each priority via
mlx5_core_access_reg().

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Mohsin Bashir <mohsin.bashr@gmail.com>
Link: https://patch.msgid.link/20260302230149.1580195-6-mohsin.bashr@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>