test: vboot: clean its file

This update the its file used in vboot test to respect the new
node style name defined in doc/uImage.FIT (for example: replace
kernel@1 by kernel and fdt@1 by fdt-1)

Signed-off-by: Philippe Reynes <philippe.reynes@softathome.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/test/py/tests/vboot/sign-configs-sha256.its b/test/py/tests/vboot/sign-configs-sha256.its
index 1b3432e..f5591aa 100644
--- a/test/py/tests/vboot/sign-configs-sha256.its
+++ b/test/py/tests/vboot/sign-configs-sha256.its
@@ -5,7 +5,7 @@
 	#address-cells = <1>;
 
 	images {
-		kernel@1 {
+		kernel {
 			data = /incbin/("test-kernel.bin");
 			type = "kernel_noload";
 			arch = "sandbox";
@@ -14,28 +14,28 @@
 			load = <0x4>;
 			entry = <0x8>;
 			kernel-version = <1>;
-			hash@1 {
+			hash-1 {
 				algo = "sha256";
 			};
 		};
-		fdt@1 {
+		fdt-1 {
 			description = "snow";
 			data = /incbin/("sandbox-kernel.dtb");
 			type = "flat_dt";
 			arch = "sandbox";
 			compression = "none";
 			fdt-version = <1>;
-			hash@1 {
+			hash-1 {
 				algo = "sha256";
 			};
 		};
 	};
 	configurations {
-		default = "conf@1";
-		conf@1 {
-			kernel = "kernel@1";
-			fdt = "fdt@1";
-			signature@1 {
+		default = "conf-1";
+		conf-1 {
+			kernel = "kernel";
+			fdt = "fdt-1";
+			signature {
 				algo = "sha256,rsa2048";
 				key-name-hint = "dev";
 				sign-images = "fdt", "kernel";