imx: mx6: fix USB bmode to use reserved value

Currently the bmode "usb" uses BOOT_CFG1 to 0x01, -which means
BOOT_CFG1[7:4] is set to b0000. According to Table 8-7 Boot
Device Selection this is NOR/OneNAND and not Reserved.

Use 0x10 which leads to b0001, which is a Reserved boot device.
With that the SoC reliably falls back to the serial loader.

Cc: Troy Kisky <troy.kisky@boundarydevices.com>
Signed-off-by: Stefan Agner <stefan.agner@toradex.com>
Tested-by: Troy Kisky <troy.kisky@boundarydevices.com>

arch/arm/cpu/armv7/mx6/soc.c

@@ -514,7 +514,7 @@ void imx_get_mac_from_fuse(int dev_id, unsigned char *mac)
 const struct boot_mode soc_boot_modes[] = {
 	{"normal",	MAKE_CFGVAL(0x00, 0x00, 0x00, 0x00)},
 	/* reserved value should start rom usb */
-	{"usb",		MAKE_CFGVAL(0x01, 0x00, 0x00, 0x00)},
+	{"usb",		MAKE_CFGVAL(0x10, 0x00, 0x00, 0x00)},
 	{"sata",	MAKE_CFGVAL(0x20, 0x00, 0x00, 0x00)},
 	{"ecspi1:0",	MAKE_CFGVAL(0x30, 0x00, 0x00, 0x08)},
 	{"ecspi1:1",	MAKE_CFGVAL(0x30, 0x00, 0x00, 0x18)},