boards: raspberrypi: rp2040-zero,xiao_rp2040: fixed inconsistencies

There were some inconsistencies in flash memory for both
of these boards where they do not match their stated specs.
This commit fixes the inconsistencies.

Signed-off-by: Nicolas Munnich <nickmunnich@gmail.com>

boards/seeed/xiao_rp2040/xiao_rp2040.dts

@@ -78,6 +78,18 @@
 		compatible = "fixed-partitions";
 		#address-cells = <1>;
 		#size-cells = <1>;
+
+		/* Reserved memory for the second stage bootloader */
+		second_stage_bootloader: partition@0 {
+			label = "second_stage_bootloader";
+			reg = <0x00000000 0x100>;
+			read-only;
+		};
+
+		/*
+		 * Usable flash. Starts at 0x100, after the bootloader. The partition
+		 * size is 2MB minus the 0x100 bytes taken by the bootloader.
+		 */
 		code_partition: partition@100 {
 			label = "code";
 			reg = <0x100 (DT_SIZE_M(2) - 0x100)>;

boards/seeed/xiao_rp2040/xiao_rp2040.yaml

@@ -3,7 +3,7 @@ name: XIAO RP2040
 type: mcu
 arch: arm
 flash: 2048
-ram: 256
+ram: 264
 toolchain:
   - zephyr
   - gnuarmemb

boards/waveshare/rp2040_zero/rp2040_zero.dts

@@ -28,7 +28,7 @@
 };
 
 &flash0 {
-	reg = <0x10000000 DT_SIZE_M(16)>;
+	reg = <0x10000000 DT_SIZE_M(2)>;
 
 	partitions {
 		compatible = "fixed-partitions";
@@ -44,11 +44,11 @@
 
 		/*
 		 * Usable flash. Starts at 0x100, after the bootloader. The partition
-		 * size is 16MB minus the 0x100 bytes taken by the bootloader.
+		 * size is 2MB minus the 0x100 bytes taken by the bootloader.
 		 */
 		code_partition: partition@100 {
 			label = "code-partition";
-			reg = <0x100 (DT_SIZE_M(16) - 0x100)>;
+			reg = <0x100 (DT_SIZE_M(2) - 0x100)>;
 			read-only;
 		};
 	};

boards/waveshare/rp2040_zero/rp2040_zero.yaml

@@ -2,7 +2,7 @@ identifier: rp2040_zero
 name: Waveshare RP2040-Zero
 type: mcu
 arch: arm
-flash: 16384
+flash: 2048
 ram: 264
 toolchain:
   - zephyr