boot: zephyr: boards: Assign boot_partition to code-patition

Include the 2M SysBuild partitions from the device-tree.

Use the boot_partition as the code-partition for RPI Pico and Pico W in
order for the SysBuild to use the boot_partition during build.

Projects using SysBuild will need to include the same 2M SysBuild
partitions and select the slot0_parition as the code-partition.  Both
slot0_partition and slot1_partitions will be used for firmware upgrade.

Signed-off-by: John Lin <john.lin@beechwoods.com>

Author: jlbwoods

boot/zephyr/boards/rpi_pico.overlay

@@ -0,0 +1,14 @@
+/*
+ * Copyright (c) 2025 Beechwoods Software Inc.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <raspberrypi/partitions_2M_sysbuild.dtsi>
+
+/ {
+	chosen {
+		/delete-property/ zephyr,code-partition;
+		zephyr,code-partition = &boot_partition;
+	};
+};

boot/zephyr/boards/rpi_pico_rp2040_w.overlay

@@ -0,0 +1 @@
+#include "rpi_pico.overlay"