When af_mpls is built-in but the tunnel support is a module,
we get a link failure:
net/mpls/af_mpls.o: In function `mpls_init':
af_mpls.c:(.init.text+0xdc): undefined reference to `ip_tunnel_encap_add_ops'
This adds a Kconfig statement to prevent the broken
configuration and force mpls to be a module as well in
this case.
Fixes: bdc476413dcd ("ip_tunnel: add mpls over gre support") Signed-off-by: Arnd Bergmann <arnd@arndb.de> Acked-by: Amine Kherbouche <amine.kherbouche@6wind.com> Signed-off-by: David S. Miller <davem@davemloft.net>