imx: imx8mm_evk: convert to OF_UPSTREAM

Convert i.MX8MM EVK to OF_UPSTREAM

Signed-off-by: Peng Fan <peng.fan@nxp.com>
diff --git a/arch/arm/mach-imx/imx8m/Kconfig b/arch/arm/mach-imx/imx8m/Kconfig
index 6f68ee2..dd139c1 100644
--- a/arch/arm/mach-imx/imx8m/Kconfig
+++ b/arch/arm/mach-imx/imx8m/Kconfig
@@ -79,6 +79,7 @@
 	select FSL_CAAM
 	select ARCH_MISC_INIT
 	select SPL_CRYPTO if SPL
+	imply OF_UPSTREAM
 
 config TARGET_IMX8MM_ICORE_MX8MM
 	bool "Engicam i.Core MX8M Mini SOM"