i.MX31: Fix architecture numbers for ADS and Litekit boards

Correct the Linux architecture number for i.MX31 Litekit and ADS boards.

Signed-off-by: Magnus Lilja <lilja.magnus@gmail.com>
diff --git a/board/mx31ads/mx31ads.c b/board/mx31ads/mx31ads.c
index a75cc2d..dd0e150 100644
--- a/board/mx31ads/mx31ads.c
+++ b/board/mx31ads/mx31ads.c
@@ -93,7 +93,7 @@
 	readb(CS4_BASE + 8);
 	readb(CS4_BASE + 7);
 
-	gd->bd->bi_arch_number = 447;		/* board id for linux */
+	gd->bd->bi_arch_number = MACH_TYPE_MX31ADS;	/* board id for linux */
 	gd->bd->bi_boot_params = 0x80000100;	/* adress of boot parameters */
 
 	return 0;