tests: fs: lib_link: add RAM disk overlay

Add a basic RAM disk overlay for libraries that expect at least one disk
driver to be enabled.

Signed-off-by: Jordan Yates <[email protected]>

Author: JordanYates

tests/subsys/fs/lib_link/app.overlay

@@ -0,0 +1,14 @@
+/*
+ * Copyright (c) 2023 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/ {
+	ramdisk0 {
+		compatible = "zephyr,ram-disk";
+		disk-name = "RAM";
+		sector-size = <512>;
+		sector-count = <80>;
+	};
+};