tg3: Move the [rt]x_dropped counters to tg3_napi

This change moves [rt]x_dropped counters to tg3_napi so that they can be
updated by a single writer, race-free.

Signed-off-by: Alex Pakhunov <alexey.pakhunov@spacex.com>
Signed-off-by: Vincent Wong <vincent.wong2@spacex.com>
Reviewed-by: Michael Chan <michael.chan@broadcom.com>
Link: https://lore.kernel.org/r/20231113182350.37472-1-alexey.pakhunov@spacex.com


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