nitrogen6x: bump U-Boot to latest production version (2013.07)

Signed-off-by: Eric Nelson <eric.nelson@boundarydevices.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

configs/nitrogen6x_defconfig

@@ -15,7 +15,7 @@ BR2_TARGET_ROOTFS_EXT2_2r1=y
 BR2_TARGET_UBOOT=y
 BR2_TARGET_UBOOT_BOARDNAME="nitrogen6q"
 BR2_TARGET_UBOOT_CUSTOM_TARBALL=y
-BR2_TARGET_UBOOT_CUSTOM_TARBALL_LOCATION="http://github.com/boundarydevices/u-boot-imx6/tarball/7176d07/u-boot-7176d07.tar.gz"
+BR2_TARGET_UBOOT_CUSTOM_TARBALL_LOCATION="http://github.com/boundarydevices/u-boot-imx6/tarball/4034391/u-boot-4034391.tar.gz"
 
 # kernel
 BR2_LINUX_KERNEL=y