If the RX descriptor doesn't have any data, the output value of quote
from rswitch_rx() will be increased unexpectedily. So, fix it.
Reported-by: NVolodymyr Babchuk <volodymyr_babchuk@epam.com>
Fixes: 3590918b ("net: ethernet: renesas: Add support for "Ethernet Switch"")
Signed-off-by: NYoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>