configs/lego_ev3: bump U-Boot version

This bumps U-Boot to the current stable version (2017.05).

Signed-off-by: David Lechner <david@lechnology.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

configs/lego_ev3_defconfig

@@ -36,7 +36,7 @@ BR2_TARGET_ROOTFS_SQUASHFS4_XZ=y
 BR2_TARGET_UBOOT=y
 BR2_TARGET_UBOOT_BUILD_SYSTEM_KCONFIG=y
 BR2_TARGET_UBOOT_CUSTOM_VERSION=y
-BR2_TARGET_UBOOT_CUSTOM_VERSION_VALUE="2016.09.01"
+BR2_TARGET_UBOOT_CUSTOM_VERSION_VALUE="2017.05"
 BR2_TARGET_UBOOT_BOARD_DEFCONFIG="legoev3"
 
 # host