net: Rename the dst_opt default_mtu method to mtu

We plan to invoke the dst_opt->default_mtu() method unconditioally
from dst_mtu(). So rename the method to dst_opt->mtu() to match
the name with the new meaning.

Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/dst_ops.h b/include/net/dst_ops.h
index 9adb998..e1c2ee0 100644
--- a/include/net/dst_ops.h
+++ b/include/net/dst_ops.h
@@ -17,7 +17,7 @@
 	int			(*gc)(struct dst_ops *ops);
 	struct dst_entry *	(*check)(struct dst_entry *, __u32 cookie);
 	unsigned int		(*default_advmss)(const struct dst_entry *);
-	unsigned int		(*default_mtu)(const struct dst_entry *);
+	unsigned int		(*mtu)(const struct dst_entry *);
 	u32 *			(*cow_metrics)(struct dst_entry *, unsigned long);
 	void			(*destroy)(struct dst_entry *);
 	void			(*ifdown)(struct dst_entry *,