configs/stm32mp157_dk_defconfig: switch to mainline 2019.07 U-Boot version

Switch to the official U-Boot repository since
the board has been officially supported.

Signed-off-by: Bartosz Bilas <b.bilas@grinn-global.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

configs/stm32mp157_dk_defconfig

@@ -18,8 +18,8 @@ BR2_TARGET_ROOTFS_EXT2_SIZE="120M"
 # BR2_TARGET_ROOTFS_TAR is not set
 BR2_TARGET_UBOOT=y
 BR2_TARGET_UBOOT_BUILD_SYSTEM_KCONFIG=y
-BR2_TARGET_UBOOT_CUSTOM_TARBALL=y
-BR2_TARGET_UBOOT_CUSTOM_TARBALL_LOCATION="$(call github,STMicroelectronics,u-boot,v2018.11-stm32mp-r2.5)/u-boot-v2018.11-stm32mp-r2.5.tar.gz"
+BR2_TARGET_UBOOT_CUSTOM_VERSION=y
+BR2_TARGET_UBOOT_CUSTOM_VERSION_VALUE="2019.07"
 BR2_TARGET_UBOOT_BOARD_DEFCONFIG="stm32mp15_basic"
 BR2_TARGET_UBOOT_CONFIG_FRAGMENT_FILES="board/stmicroelectronics/stm32mp157-dk/uboot-fragment.config"
 # BR2_TARGET_UBOOT_FORMAT_BIN is not set