netif_rx() only returns NET_RX_DROP and NET_RX_SUCCESS, not returns
negative value
Signed-off-by: NLi RongQing <roy.qing.li@gmail.com>
Acked-by: NJukka Rissanen <jukka.rissanen@linux.intel.com>
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>