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/imx31_litekit/imx31_litekit.c b/board/imx31_litekit/imx31_litekit.c
index 5ba60e9..e0fbf25 100644
--- a/board/imx31_litekit/imx31_litekit.c
+++ b/board/imx31_litekit/imx31_litekit.c
@@ -52,7 +52,7 @@
 	mx31_gpio_mux(MUX_RTS1__UART1_RTS_B);
 	mx31_gpio_mux(MUX_RTS1__UART1_CTS_B);
 
-	gd->bd->bi_arch_number = 447;		/* board id for linux */
+	gd->bd->bi_arch_number = MACH_TYPE_MX31LITE; /* board id for linux */
 	gd->bd->bi_boot_params = (0x80000100);	/* adress of boot parameters */
 
 	return 0;