net: lan966x: Fix spelling mistake "tarffic" -> "traffic"

There is a spelling mistake in a netdev_err message. Fix it.

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Reviewed-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>