net: Export auto_load, use it in rarp

The rarp code includes another instance of the auto_load logic, so call
what is now net_auto_load() instead.

This also fixes an incorrect call to TftpStart() which was never seen
since apparently no boards enable rarp.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Mike Frysinger <vapier@gentoo.org>

include/net.h

@@ -429,6 +429,12 @@ extern int	NetSendUDPPacket(uchar *ether, IPaddr_t dest, int dport, int sport, i
 /* Processes a received packet */
 extern void	NetReceive(volatile uchar *, int);
 
+/*
+ * Check if autoload is enabled. If so, use either NFS or TFTP to download
+ * the boot file.
+ */
+void net_auto_load(void);
+
 /*
  * The following functions are a bit ugly, but necessary to deal with
  * alignment restrictions on ARM.