Fixed return value evaluation on DTT I2C operation

Signed-off-by: Roland Stigge <stigge@debian.org>

--- u-boot/dtt/lm81.c.orig	2007-06-16 11:55:04.000000000 +0200
+++ u-boot/dtt/lm81.c	2007-06-16 11:55:24.000000000 +0200
@@ -108,7 +108,7 @@
 	if (adr < 0)
 		return 1;
 	rev = dtt_read (sensor, DTT_REV);
-	if (adr < 0)
+	if (rev < 0)
 		return 1;
 
 	printf ("DTT:   Found LM81@%x Rev: %d\n", adr, rev);