binman: Allow the image name to be the data file

Some image types use the -n parameter to pass in the data file. Add
support for this, with a new property.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/binman/test/235_mkimage_name.dts b/tools/binman/test/235_mkimage_name.dts
new file mode 100644
index 0000000..fbc82f1
--- /dev/null
+++ b/tools/binman/test/235_mkimage_name.dts
@@ -0,0 +1,18 @@
+// SPDX-License-Identifier: GPL-2.0+
+
+/dts-v1/;
+
+/ {
+	#address-cells = <1>;
+	#size-cells = <1>;
+
+	binman {
+		mkimage {
+			args = "-T script";
+			data-to-imagename;
+
+			u-boot-spl {
+			};
+		};
+	};
+};