beaglebone: update to latest U-Boot

Update to the default version of U-Boot, at this time 2013.10.

Tested with an old uEnv.txt (i.e. using uImage) and with the
currently prefered zImage.

Signed-off-by: Anders Darander <anders@chargestorm.se>
Reviewed-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

configs/beaglebone_defconfig

@@ -22,7 +22,7 @@ BR2_DEFAULT_KERNEL_VERSION="3.12.10"
 BR2_TARGET_UBOOT=y
 BR2_TARGET_UBOOT_BOARDNAME="am335x_evm"
 BR2_TARGET_UBOOT_CUSTOM_VERSION=y
-BR2_TARGET_UBOOT_CUSTOM_VERSION_VALUE="2013.04"
+BR2_TARGET_UBOOT_CUSTOM_VERSION_VALUE="2013.10"
 BR2_TARGET_UBOOT_FORMAT_IMG=y
 BR2_TARGET_UBOOT_SPL=y
 BR2_TARGET_UBOOT_SPL_NAME="MLO"