configs/lego_ev3: add U-Boot support

This adds U-Boot configuration for LEGO MINDSTORMS EV3. U-Boot has
had support for LEGO MINDSTORMS EV3 since v2016.05.

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

configs/lego_ev3_defconfig

@@ -24,3 +24,10 @@ BR2_LINUX_KERNEL_UIMAGE=y
 BR2_TARGET_ROOTFS_EXT2=y
 BR2_TARGET_ROOTFS_EXT2_3=y
 # BR2_TARGET_ROOTFS_TAR is not set
+
+# U-Boot
+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_BOARD_DEFCONFIG="legoev3"