expo: Update tests to include textline

Provide test coverage for the new expo object type, including building
and reading/writing settings.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/test/boot/files/expo_layout.dts b/test/boot/files/expo_layout.dts
index cb2a674..bed5522 100644
--- a/test/boot/files/expo_layout.dts
+++ b/test/boot/files/expo_layout.dts
@@ -55,6 +55,14 @@
 				start-bit = <0x422>;
 				bit-length = <2>;
 			};
+
+			machine-name {
+				id = <ID_MACHINE_NAME>;
+				type = "textline";
+				max-chars = <20>;
+				title = "Machine name";
+				edit-id = <ID_MACHINE_NAME_EDIT>;
+			};
 		};
 	};