net: if_arp: add ARPHRD_6LOWPAN type

Used for IPv6 over LoWPAN networks. Example of this is
Bluetooth 6LoWPAN network.
Signed-off-by: NJukka Rissanen <jukka.rissanen@linux.intel.com>
Acked-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>

include/uapi/linux/if_arp.h

@@ -94,6 +94,7 @@
 #define ARPHRD_CAIF	822		/* CAIF media type		*/
 #define ARPHRD_IP6GRE	823		/* GRE over IPv6		*/
 #define ARPHRD_NETLINK	824		/* Netlink header		*/
+#define ARPHRD_6LOWPAN	825		/* IPv6 over LoWPAN             */
 
 #define ARPHRD_VOID	  0xFFFF	/* Void type, nothing is known */
 #define ARPHRD_NONE	  0xFFFE	/* zero header length */