net/mlx5e: Report rx_discards_phy via rx_dropped

net/mlx5e: Report rx_discards_phy via rx_dropped

We noticed a high number of rx_discards_phy events on certain servers while
running `ethtool -S`. However, this critical counter is not currently
included in the standard /proc/net/dev statistics file, making it difficult
to monitor effectively—especially given the diversity of vendors across a
large fleet of servers.

Let's report it via the standard rx_dropped metric.

Suggested-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Cc: Saeed Mahameed <saeedm@nvidia.com>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Gal Pressman <gal@nvidia.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://patch.msgid.link/20241210022706.6665-1-laoar.shao@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>