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>

net/rarp.c

@@ -46,24 +46,8 @@ static void
 RarpHandler(uchar *dummi0, unsigned dummi1, IPaddr_t sip, unsigned dummi2,
 	    unsigned dummi3)
 {
-	char *s;
 	debug("Got good RARP\n");
-	if ((s = getenv("autoload")) != NULL) {
-		if (*s == 'n') {
-			/*
-			 * Just use RARP to configure system;
-			 * Do not use TFTP/NFS to to load the bootfile.
-			 */
-			NetState = NETLOOP_SUCCESS;
-			return;
-#if defined(CONFIG_CMD_NFS)
-		} else if ((s != NULL) && !strcmp(s, "NFS")) {
-			NfsStart();
-			return;
-#endif
-		}
-	}
-	TftpStart ();
+	net_auto_load();
 }