Signed configurations

/dts-v1/;
/ {
 description = "Chrome OS kernel image with one or more FDT blobs";
 #address-cells = <1>;
 images {
 kernel {
 data = /incbin/("test-kernel.bin");
 type = "kernel_noload";
 arch = "sandbox";
 os = "linux";
 compression = "lzo";
 load = <0x4>;
 entry = <0x8>;
 kernel-version = <1>;
 hash-1 {
 algo = "sha256";
 };
 };
 fdt-1 {
 description = "snow";
 data = /incbin/("sandbox-kernel.dtb");
 type = "flat_dt";
 arch = "sandbox";
 compression = "none";
 fdt-version = <1>;
 hash-1 {
 algo = "sha256";
 };
 };
 };
 configurations {
 default = "conf-1";
 conf-1 {
 kernel = "kernel";
 fdt = "fdt-1";
 signature {
 algo = "sha256,rsa2048";
 key-name-hint = "dev";
 sign-images = "fdt", "kernel";
 };
 };
 };
};