ip_tunnel: Provide tunnel metadata API for CONFIG_INET=n
Account for the configuration FIB_RULES=y && INET=n as FIB_RULES can
be selected by IPV6 or DECNET without INET.
Fixes: e2d53df124c4 ("fib: Add fib rule match on tunnel id") Fixes: f232b2dc245c ("route: Per route IP tunnel metadata via lightweight tunnel") Reported-by: kbuild test robot <fengguang.wu@intel.com> Signed-off-by: Thomas Graf <tgraf@suug.ch> Signed-off-by: David S. Miller <davem@davemloft.net>