imx8mn_ddr4_evk: Allow booting the kernel by default

Currently it is not possible to boot Linux from the SD card
by default.

Make the necessary adjustments to allow it.
Reported-by: NPeter Bergin <peter@berginkonsult.se>
Signed-off-by: NFabio Estevam <festevam@gmail.com>
Tested-by: Andrey Zhizhikin <andrey.z@gmail.com> # imx8mn_ddr4_evk
Reviewed-by: NPeng Fan <peng.fan@nxp.com>

configs/imx8mn_ddr4_evk_defconfig

@@ -54,6 +54,7 @@ CONFIG_SPL_OF_CONTROL=y
 CONFIG_ENV_OVERWRITE=y
 CONFIG_ENV_IS_IN_MMC=y
 CONFIG_SYS_RELOC_GD_ENV_ADDR=y
+CONFIG_SYS_MMC_ENV_DEV=1
 CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG=y
 CONFIG_SPL_DM=y
 CONFIG_SPL_CLK_COMPOSITE_CCF=y

include/configs/imx8mn_evk.h

@@ -34,10 +34,10 @@
 /* Initial environment variables */
 #define CONFIG_EXTRA_ENV_SETTINGS		\
 	"script=boot.scr\0" \
-	"image=Image.itb\0" \
+	"image=Image\0" \
 	"console=ttymxc1,115200\0" \
 	"fdt_addr=0x43000000\0"			\
-	"boot_fit=try\0" \
+	"boot_fit=no\0" \
 	"fdt_file=" CONFIG_DEFAULT_FDT_FILE "\0" \
 	"initrd_addr=0x43800000\0"		\
 	"bootm_size=0x10000000\0" \