ARM: dts: stm32: convert stm32mp13 board to OF_UPSTREAM

Enable OF_UPSTREAM flag for STM32MP13 platforms.

Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>
Reviewed-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
diff --git a/arch/arm/mach-stm32mp/Kconfig b/arch/arm/mach-stm32mp/Kconfig
index 002da2e..3a5f488 100644
--- a/arch/arm/mach-stm32mp/Kconfig
+++ b/arch/arm/mach-stm32mp/Kconfig
@@ -52,6 +52,7 @@
 	select STM32_SERIAL
 	select SYS_ARCH_TIMER
 	imply CMD_NVEDIT_INFO
+	imply OF_UPSTREAM
 	help
 		support of STMicroelectronics SOC STM32MP13x family
 		STMicroelectronics MPU with core ARMv7