ehci(4): Fix bug causing missed wakeups since ehci.c 1.308.

For reasons beyond me now, I used cv_signal on the same cv that is
used to wait for the doorbell to be available _and_ to wait for the
host controller to acknowledge the doorbell.  Which means when the
host controller acknowledges the doorbell, we might wake some thread
waiting for the doorbell to be available -- and leave the thread
waiting for the doorbell acknowledgment hanging indefinitely.

PR port-i386/57662

XXX pullup-10

sys/dev/usb/ehci.c

@@ -1,4 +1,4 @@
-/*	$NetBSD: ehci.c,v 1.318 2023/10/28 21:18:15 riastradh Exp $ */
+/*	$NetBSD: ehci.c,v 1.319 2023/10/28 21:18:31 riastradh Exp $ */
 
 /*
  * Copyright (c) 2004-2012,2016,2020 The NetBSD Foundation, Inc.
@@ -54,7 +54,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: ehci.c,v 1.318 2023/10/28 21:18:15 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: ehci.c,v 1.319 2023/10/28 21:18:31 riastradh Exp $");
 
 #include "ohci.h"
 #include "uhci.h"
@@ -826,7 +826,7 @@ ehci_doorbell(void *addr)
 	if (sc->sc_doorbelllwp == NULL)
 		DPRINTF("spurious doorbell interrupt", 0, 0, 0, 0);
 	sc->sc_doorbelllwp = NULL;
-	cv_signal(&sc->sc_doorbell);
+	cv_broadcast(&sc->sc_doorbell);
 	mutex_exit(&sc->sc_lock);
 }
 
@@ -2279,7 +2279,7 @@ ehci_sync_hc(ehci_softc_t *sc)
 		now = getticks();
 		if (now - starttime >= delta) {
 			sc->sc_doorbelllwp = NULL;
-			cv_signal(&sc->sc_doorbell);
+			cv_broadcast(&sc->sc_doorbell);
 			DPRINTF("doorbell timeout", 0, 0, 0, 0);
 #ifdef DIAGNOSTIC		/* XXX DIAGNOSTIC abuse, do this differently */
 			printf("ehci_sync_hc: timed out\n");