armv8: sec_firmware: Add support for multiple loadables

Enable support for multiple loadable images in SEC firmware FIT image.
Also add example "sec_firmware_ppa.its" file.

Signed-off-by: Sumit Garg <sumit.garg@nxp.com>
Reviewed-by: York Sun <york.sun@nxp.com>

doc/uImage.FIT/sec_firmware_ppa.its

@@ -0,0 +1,49 @@
+/dts-v1/;
+
+/*
+ * Example FIT image description file demonstrating the usage
+ * of SEC Firmware and multiple loadable images loaded by the u-boot.
+ * For booting PPA (SEC Firmware), "firmware" is searched and loaded.
+ *
+ * Multiple binaries will be loaded as "loadables" (if present) at their
+ * respective load offsets from firmware image address.
+ */
+
+/{
+	description = "PPA Firmware";
+	#address-cells = <1>;
+	images {
+		firmware@1 {
+			description = "PPA Firmware: <version>";
+			data = /incbin/("../obj/monitor.bin");
+			type = "firmware";
+			arch = "arm64";
+			compression = "none";
+		};
+		trustedOS@1 {
+			description = "Trusted OS";
+			data = /incbin/("../../tee.bin");
+			type = "OS";
+			arch = "arm64";
+			compression = "none";
+			load = <0x00200000>;
+		};
+		fuse_scr {
+			description = "Fuse Script";
+			data = /incbin/("../../fuse_scr.bin");
+			type = "firmware";
+			arch = "arm64";
+			compression = "none";
+			load = <0x00180000>;
+		};
+	};
+
+	configurations {
+		default = "config-1";
+		config-1 {
+			description = "PPA Secure firmware";
+			firmware = "firmware@1";
+			loadables = "trustedOS@1", "fuse_scr";
+		};
+	};
+};