configs: colibri_imx7: use separate device tree

Use OF_SEPARATE as suggested by the build system.

Signed-off-by: Stefan Agner <stefan.agner@toradex.com>
Acked-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
diff --git a/configs/colibri_imx7_defconfig b/configs/colibri_imx7_defconfig
index a24620a..b919a29 100644
--- a/configs/colibri_imx7_defconfig
+++ b/configs/colibri_imx7_defconfig
@@ -44,7 +44,6 @@
 CONFIG_MTDPARTS_DEFAULT="mtdparts=gpmi-nand:512k(mx7-bcb),1536k(u-boot1)ro,1536k(u-boot2)ro,512k(u-boot-env),-(ubi)"
 CONFIG_CMD_UBI=y
 CONFIG_OF_CONTROL=y
-CONFIG_OF_EMBED=y
 CONFIG_DEFAULT_DEVICE_TREE="imx7-colibri-rawnand"
 CONFIG_ENV_IS_IN_NAND=y
 CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG=y