rp2040: Add rp2350 bootrom based chipid and reboot to bootloader code

This adds the bootrom code needed to implement "reboot into
bootloader" and "chipid" capabilities.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

src/rp2040/main.c

@@ -49,9 +49,7 @@ bootloader_request(void)
 {
     watchdog_hw->ctrl = 0;
     try_request_canboot();
-    // Use the bootrom-provided code to reset into BOOTSEL mode
-    if (CONFIG_MACH_RP2040)
-        bootrom_reboot_usb_bootloader();
+    bootrom_reboot_usb_bootloader();
 }