RP2040 Enter uf2 DFU mode (#3062)

* Pico enter dfu mode

* Ungaurd pico

src/platform/rp2040/main-rp2040.cpp

@@ -35,4 +35,9 @@ void rp2040Setup()
        Taken from CPU cycle counter and ROSC oscillator, so should be pretty random.
     */
     randomSeed(rp2040.hwrand32());
+}
+
+void enterDfuMode()
+{
+    reset_usb_boot(0, 0);
 }