samples : subsys : littlefs: Add overlay files for Pico and Pico_w

Add a 16 KB 'storage' partition at the end of the Pico flash. That size is sufficient to hold the two
test files created by this sample.

Signed-off-by: Andreas Wolf <awolf002@gmail.com>

Author: Snap-A

samples/subsys/fs/littlefs/boards/rpi_pico.overlay

@@ -1,21 +1,26 @@
+/*
+ * Copyright (c) 2025 Andreas Wolf <awolf002@gmail.com>
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
 
 /delete-node/ &code_partition;
 
 &flash0 {
-    partitions {
-        compatible = "fixed-partitions";
-        #address-cells = <1>;
-        #size-cells = <1>;
+	partitions {
+		compatible = "fixed-partitions";
+		#address-cells = <1>;
+		#size-cells = <1>;
 
-        code_partition: partition@100 {
-            label = "code-partition";
-            reg = <0x100 (DT_SIZE_M(2)-0x100-DT_SIZE_K(64))>;
-            read-only;
-        };
+		code_partition: partition@100 {
+			label = "code-partition";
+			reg = <0x100 (DT_SIZE_M(2) - 0x100 - DT_SIZE_K(16))>;
+			read-only;
+		};
 
-        storage_partition: storage_partition@1f0000 {
-            label = "storage-partition";
-            reg = <(DT_SIZE_M(2)-DT_SIZE_K(64)) (DT_SIZE_K(64))>;
-        };
-    };
+		storage_partition: storage_partition@1f0000 {
+			label = "storage-partition";
+			reg = <(DT_SIZE_M(2) - DT_SIZE_K(16)) (DT_SIZE_K(16))>;
+		};
+	};
 };

samples/subsys/fs/littlefs/boards/rpi_pico_rp2040_w.overlay

@@ -1 +1,7 @@
+/*
+ * Copyright (c) 2025 Andreas Wolf <awolf002@gmail.com>
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
 #include "rpi_pico.overlay"