arm: fsl: imx8mn_bsh_smm_s2: Migrate to OF_UPSTREAM

Migrate imx8mn_bsh_smm_s2 and imx8mn_bsh_smm_s2pro boards to OF_UPSTREAM.

Signed-off-by: Patrick Barsanti <patrick.barsanti@amarulasolutions.com>
Tested-by: Michael Trimarchi <michael@amarulasolutions.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
diff --git a/arch/arm/mach-imx/imx8m/Kconfig b/arch/arm/mach-imx/imx8m/Kconfig
index 046c785..d1fdaec 100644
--- a/arch/arm/mach-imx/imx8m/Kconfig
+++ b/arch/arm/mach-imx/imx8m/Kconfig
@@ -137,12 +137,14 @@
 	select IMX8MN
 	select SUPPORT_SPL
 	select IMX8M_DDR3L
+	imply OF_UPSTREAM
 
 config TARGET_IMX8MN_BSH_SMM_S2PRO
 	bool "imx8mn-bsh-smm-s2pro"
 	select IMX8MN
 	select SUPPORT_SPL
 	select IMX8M_DDR3L
+	imply OF_UPSTREAM
 
 config TARGET_IMX8MN_EVK
 	bool "imx8mn LPDDR4 EVK board"