include/uapi/linux/sockios.h: mark SIOCRTMSG unused

IOCTL SIOCRTMSG does nothing but return EINVAL.

So comment it as unused.

SIOCRTMSG is only used in:
* net/ipv4/af_inet.c
* include/uapi/linux/sockios.h

inet_ioctl calls ip_rt_ioctl.
ip_rt_ioctl only handles SIOCADDRT and SIOCDELRT and returns -EINVAL
otherwise.
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/uapi/linux/sockios.h

@@ -27,7 +27,7 @@
 /* Routing table calls. */
 #define SIOCADDRT	0x890B		/* add routing table entry	*/
 #define SIOCDELRT	0x890C		/* delete routing table entry	*/
-#define SIOCRTMSG	0x890D		/* call to routing system	*/
+#define SIOCRTMSG	0x890D		/* unused			*/
 
 /* Socket configuration controls. */
 #define SIOCGIFNAME	0x8910		/* get iface name		*/