net: ravb: Count packets instead of descriptors in GbEth RX path

The units of "work done" in the RX path should be packets instead of
descriptors, as large packets can be spread over multiple descriptors.

Fixes: 1c59eb67 ("ravb: Fillup ravb_rx_gbeth() stub")
Signed-off-by: Paul Barker <paul.barker.ct@bp.renesas.com>
Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Link: https://lore.kernel.org/r/20240214151204.2976-1-paul.barker.ct@bp.renesas.com


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