gnrc_ndp2: rename to gnrc_ndp

Makefile.dep

sys/include/net/gnrc/ndp.h

sys/include/net/gnrc/netif.h

sys/net/gnrc/Makefile

sys/net/gnrc/netif/gnrc_netif_ieee802154.c

sys/net/gnrc/network_layer/ipv6/nib/_nib-6ln.c

sys/net/gnrc/network_layer/ipv6/nib/_nib-arsm.c

sys/net/gnrc/network_layer/ipv6/nib/_nib-router.c

sys/net/gnrc/network_layer/ipv6/nib/nib.c

sys/net/gnrc/network_layer/ndp/Makefile

sys/net/gnrc/network_layer/ndp/gnrc_ndp.c

sys/net/gnrc/network_layer/sixlowpan/nd/gnrc_sixlowpan_nd.c

...work_layer/sixlowpan/nd/router/gnrc_sixlowpan_nd_router.c

tests/gnrc_ipv6_nib/Makefile

tests/gnrc_ipv6_nib/mockup_netif.c

tests/gnrc_ipv6_nib_6ln/Makefile

tests/gnrc_ipv6_nib_6ln/mockup_netif.c

tests/gnrc_ndp/Makefile

tests/gnrc_ndp/main.c

tests/gnrc_ndp/tests/01-run.py