eth: fbnic: Lock the tx_dropped update

Wrap copying of drop stats on TX path from fbd->hw_stats by the
hw_stats_lock. Currently, it is being performed outside the lock and
another thread accessing fbd->hw_stats can lead to inconsistencies.

Fixes: 5f8bd2ce ("eth: fbnic: add support for TMI stats")
Signed-off-by: Mohsin Bashir <mohsin.bashr@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250802024636.679317-3-mohsin.bashr@gmail.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>