net: Move ARP out of net.c

Separate this functionality out of the net.c behemoth

Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>
Acked-by: Simon Glass <sjg@chromium.org>
Acked-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/include/net.h b/include/net.h
index 453231b..64700d9 100644
--- a/include/net.h
+++ b/include/net.h
@@ -428,7 +428,8 @@
 extern int	NetCksumOk(uchar *, int);	/* Return true if cksum OK */
 extern uint	NetCksum(uchar *, int);		/* Calculate the checksum */
 
-/* Set callbacks */
+/* Callbacks */
+extern rxhand_f *NetGetHandler(void);		/* Get RX packet handler */
 extern void	NetSetHandler(rxhand_f *);	/* Set RX packet handler */
 extern void net_set_icmp_handler(rxhand_icmp_f *f); /* Set ICMP RX handler */
 extern void	NetSetTimeout(ulong, thand_f *);/* Set timeout handler */