dcd/musb: clear rxrdy_consumed when stalling EP0

The actual-STALL path (no deferred SETUP) forced EP0 to IDLE but left
rxrdy_consumed set if the aborted transfer had parked RXRDY via NAK flow
control (e.g. a rejected OUT-data request in DATA_OUT). A subsequent
SETUP IRQ would then hit the parked-gate early return and be ignored,
relying on SentStall/SetupEnd to clear the flag first. Clear it here
so recovery never depends on that ordering.

Addresses Copilot review on #3699.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/portable/mentor/musb/dcd_musb.c

@@ -944,6 +944,9 @@ void dcd_edpt_stall(uint8_t rhport, uint8_t ep_addr) {
         // would land on that innocent request. Skip the stall and replay the deferred SETUP instead.
         pipe0_process_deferred_setup(rhport, ep_csr, false);
       } else {
+        // Forcing EP0 to IDLE: any RXRDY parked by the aborted transfer's flow control is stale,
+        // clear it so the next SETUP IRQ is not gated off.
+        _dcd.pipe0.rxrdy_consumed = false;
         ep_csr->csr0l = MUSB_CSRL0_STALL;
       }
     }