wch: recover the CH569 link when the deferred re-init is dropped

usb30_bus_reset_from_isr() deinits the controller and then latches
_hw_reinit_deferred only if usbd_defer_func() actually queued the work. When the
usbd event queue is full the deferral is dropped - and nothing else can ever run
it, because usb30_hw_deinit() has already zeroed LINK_INT_CTRL, so the dispatch
test in dcd_int_handler is permanently false and no LINK interrupt can arrive to
retry. Without the fallback ladder (the default) there is no timer either, and
with it FB_USB3_UP has already stopped TMR0. The port stayed off the bus until
the next dcd_init.

The partner-gone caller queues DCD_EVENT_UNPLUGGED one line earlier, so a single
free slot is enough to lose the re-init. Fall back to settling inline when the
deferral fails: ~30 ms in the ISR only on a full queue, versus losing the device.

src/portable/wch/dcd_ch56x_usb30.c

@@ -250,6 +250,17 @@ static void usb30_bus_reset_from_isr(void) {
   // queue is full, and a latch set for a call that was dropped would block every later re-init
   // (and make the fallback tick skip its own recovery) for good.
   _hw_reinit_deferred = usbd_defer_func(usb30_hw_reinit_task, NULL, true);
+  if (!_hw_reinit_deferred) {
+    // The deferral was dropped, and nothing else will ever run it: usb30_hw_deinit() above
+    // zeroed LINK_INT_CTRL, so the dispatch test in dcd_int_handler can never be true again and
+    // no LINK interrupt can arrive to retry. Without the fallback ladder (the default) there is
+    // no timer either, and with it FB_USB3_UP has already stopped TMR0 - so the port would stay
+    // off the bus until the next dcd_init. Pay the settle inline instead: ~30 ms in the ISR is
+    // far cheaper than losing the device, and this only happens when the event queue is full.
+    link_delay_us(30000);
+    USBSS->LINK_INT_FLAG = 0xFFFFFFFFu;
+    usb30_hw_init();
+  }
 }
 
 // Reset endpoint/transfer bookkeeping when the link (re)trains