net: ipv6: set route type for anycast routes

Anycast routes have the RTF_ANYCAST flag set, but when dumping routes
for userspace the route type is not set to RTN_ANYCAST. Make it so.

Fixes: 58c4fb86

 ("[IPV6]: Flag RTF_ANYCAST for anycast routes")
CC: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>