batman-adv: Return error codes instead of -1 on failures

Signed-off-by: Sven Eckelmann <sven@narfation.org>

diff --cc net/batman-adv/bat_debugfs.c
Simple merge

diff --cc net/batman-adv/bat_iv_ogm.c
Simple merge

diff --cc net/batman-adv/bat_sysfs.c
Simple merge

diff --cc net/batman-adv/bridge_loop_avoidance.c
Simple merge

diff --cc net/batman-adv/hard-interface.c
Simple merge

diff --cc net/batman-adv/icmp_socket.c
Simple merge

diff --cc net/batman-adv/main.c
Simple merge

diff --cc net/batman-adv/originator.c
Simple merge

diff --cc net/batman-adv/translation-table.c
Simple merge

diff --cc net/batman-adv/vis.c
Simple merge