net: bcmgenet: count hw discarded packets in missed stat

Hardware discarded packets are now counted in their own missed stat
instead of being lumped in with general errors.

Signed-off-by: Zak Kemble <zakkemble@gmail.com>
Tested-by: Florian Fainelli <florian.fainelli@broadcom.com>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Link: https://patch.msgid.link/20250519113257.1031-3-zakkemble@gmail.com


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