[IPV6] SYSCTL: complete initialization for sysctl table in subsystem code.

Move initialization bits for subsystem sysctl tables to
appropriate functions.
 - route
 - icmp

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>

diff --cc net/ipv6/icmp.c
Simple merge

diff --cc net/ipv6/route.c
Simple merge

diff --cc net/ipv6/sysctl_net_ipv6.c
Simple merge