Both netinet/icmp6.h and linux/in6.h will define struct in6_addr, and in
user space we want to use the netinet/icmp6.h variant.
Fixes build problem:
In file included from src/libsystemd-network/sd-radv.c:23:0:
/home/hegtvedt/work/os/product/sunrise/root/_build/v2/include/linux/in6.h:30:8:
error: redefinition of 'struct in6_addr'
Change-Id: I5e36d3a8a2f73681241436ab02fec4440a6a1902
#include <netinet/icmp6.h>
#include <netinet/in.h>
#include <arpa/inet.h>
-#include <linux/in6.h>
#include "sd-radv.h"