staging: octeon-ethernet: make dropped packets to consume NAPI budget

We should count also dropped packets, otherwise the NAPI handler may
end up running too long.

Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Acked-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>