ARM: dts: stm32: convert stm23h7 boards to OF_UPSTREAM

Enable OF_UPSTREAM flag for STM32H7 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-stm32/Kconfig b/arch/arm/mach-stm32/Kconfig
index a44ebf2..0824ee3 100644
--- a/arch/arm/mach-stm32/Kconfig
+++ b/arch/arm/mach-stm32/Kconfig
@@ -51,6 +51,7 @@
 	select STM32_TIMER
 	select SYSCON
 	select TIMER
+	imply OF_UPSTREAM
 
 source "arch/arm/mach-stm32/stm32f4/Kconfig"
 source "arch/arm/mach-stm32/stm32f7/Kconfig"