usbd: clear the queued-setup counter on bus reset

A SETUP counted before a bus reset must not be carried across it: the
consumer would either skip a post-reset SETUP (count drained by the
stale entry) or, if the count leaked high for any other reason, skip
them all. usbd_reset() now zeroes the counter; the consumer already
guards on zero, and any pre-reset SETUP still in the queue is stale by
definition and correctly discarded.

src/device/usbd.c

diff --git a/src/device/usbd.c b/src/device/usbd.c
index b77b766..79802e7 100644
--- a/src/device/usbd.c
+++ b/src/device/usbd.c
@@ -642,6 +642,8 @@
 
 static void usbd_reset(uint8_t rhport) {
   configuration_reset(rhport);
+  // discard any pre-reset SETUP still counted: a stale count skips post-reset SETUPs
+  _usbd_queued_setup = 0;
 }
 
 bool tud_task_event_ready(void) {