configs: imx8qm/qxp_mek: enable CONFIG_OF_SYSTEM_SETUP

Enable CONFIG_OF_SYSTEM_SETUP to let U-Boot could disable
device tree nodes that could not be used by Linux.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
diff --git a/configs/imx8qm_mek_defconfig b/configs/imx8qm_mek_defconfig
index ee29be4..57cf659 100644
--- a/configs/imx8qm_mek_defconfig
+++ b/configs/imx8qm_mek_defconfig
@@ -15,6 +15,7 @@
 CONFIG_SPL_DRIVERS_MISC_SUPPORT=y
 CONFIG_NR_DRAM_BANKS=3
 CONFIG_SPL=y
+CONFIG_OF_SYSTEM_SETUP=y
 CONFIG_SYS_EXTRA_OPTIONS="IMX_CONFIG=board/freescale/imx8qm_mek/imximage.cfg"
 CONFIG_BOOTDELAY=3
 CONFIG_LOG=y