verdin-imx8mm: enable fdt overlays and env importing

Enable CONFIG_CMD_IMPORTENV and CONFIG_OF_LIBFDT_OVERLAY needed
for booting regular Toradex BSP images.

Signed-off-by: Igor Opaniuk <igor.opaniuk@toradex.com>
Reviewed-by: Oleksandr Suvorov <oleksandr.suvorov@toradex.com>
diff --git a/configs/verdin-imx8mm_defconfig b/configs/verdin-imx8mm_defconfig
index 7ebfd67..531d566 100644
--- a/configs/verdin-imx8mm_defconfig
+++ b/configs/verdin-imx8mm_defconfig
@@ -41,7 +41,6 @@
 # CONFIG_BOOTM_NETBSD is not set
 CONFIG_CMD_ASKENV=y
 # CONFIG_CMD_EXPORTENV is not set
-# CONFIG_CMD_IMPORTENV is not set
 # CONFIG_CMD_CRC32 is not set
 CONFIG_CMD_MEMTEST=y
 CONFIG_SYS_MEMTEST_START=0x40000000
@@ -103,3 +102,4 @@
 CONFIG_SYSRESET_WATCHDOG=y
 CONFIG_DM_THERMAL=y
 CONFIG_IMX_WATCHDOG=y
+CONFIG_OF_LIBFDT_OVERLAY=y