sh: Fix get_wchan().

Some time ago the schedule frame size changed and we failed to reflect
this in get_wchan() at the time. This first popped up as a problem on
SH7751R where schedule_frame ended up being unaligned and generating
an unaligned trap. This fixes it up again..
Signed-off-by: NPaul Mundt <lethal@linux-sh.org>

arch/sh/kernel/process.c

@@ -470,9 +470,10 @@ unsigned long get_wchan(struct task_struct *p)
 	 */
 	pc = thread_saved_pc(p);
 	if (in_sched_functions(pc)) {
-		schedule_frame = ((unsigned long *)(long)p->thread.sp)[1];
-		return (unsigned long)((unsigned long *)schedule_frame)[1];
+		schedule_frame = (unsigned long)p->thread.sp;
+		return ((unsigned long *)schedule_frame)[21];
 	}
+
 	return pc;
 }