fngsystem: Load fdt file and overlays directly from fitImage

This way it's the same procedure as for normal Yocto image (picked from boot_conf environment variable).

Now we can remove the separate dtb and dtbo files from the fngsystem image.

recipes-bsp/u-boot/files/boot.script

@@ -85,7 +85,8 @@ for BOOT_SLOT in "${TMP_BOOT_ORDER}"; do
             fatload mmc 0:3 ${kernel_addr_r} fitImage
             fatload mmc 0:3 ${ramdisk_addr_r} fngsystem-image.cpio.gz
             setenv ramdisk "${ramdisk_addr_r}:${filesize}"
-            fatload mmc 0:3 ${fdt_addr_r} ${fdtfile}
+
+            env exists boot_conf || setenv boot_conf "${fdt_boot_conf}"
 
             setenv bootargs "${default_bootargs} root=/dev/mmcblk0p3 rauc.slot=alternative"
         fi
@@ -163,7 +164,7 @@ fi
 
 echo "Starting Kernel ..."
 if test -n "${ramdisk}"; then
-    bootm ${kernel_addr_r} $ramdisk ${fdt_addr_r}
+    bootm ${kernel_addr_r}${boot_conf} $ramdisk
 else
     bootm ${kernel_addr_r}${boot_conf}
 fi