libthread: drop schedlock

Having two locks in the proc was causing deadlocks.

src/libthread/thread.c

@@ -281,7 +281,7 @@ static void
 pthreadwakeupschedlocked(Proc *p, _Thread *self, _Thread *t)
 {
 	_threaddebug(self, "pthreadwakeupschedlocked %p %d", p, t->id);;
-	t->schedrend.l = &p->schedlock;
+	t->schedrend.l = &p->lock;
 	p->schedthread = t;
 	_procwakeup(&t->schedrend);
 }

src/libthread/threadimpl.h

@@ -88,7 +88,6 @@ struct Proc
 	uint		nthread;
 	uint		sysproc;
 	_Procrendez	runrend;
-	Lock		schedlock;
 	_Thread	*schedthread;
 	void		*udata;
 	Jmp		sigjmp;