batman-adv: rename batman_if struct to hard_iface

net/batman-adv/aggregation.c

net/batman-adv/aggregation.h

net/batman-adv/bat_sysfs.c

net/batman-adv/hard-interface.c

net/batman-adv/hard-interface.h

net/batman-adv/main.c

net/batman-adv/originator.c

net/batman-adv/originator.h

net/batman-adv/routing.c

net/batman-adv/routing.h

net/batman-adv/send.c

net/batman-adv/send.h

net/batman-adv/soft-interface.c

net/batman-adv/soft-interface.h

net/batman-adv/types.h

net/batman-adv/unicast.c

net/batman-adv/unicast.h

net/batman-adv/vis.c