Blackfin: do not try displaying the end of the stack

The end of the stack may not be valid (and that could be OK), so do not
attempt to parse it.  If we do, we might use a bad pointer in kernel space
which makes things panic().
Signed-off-by: NSonic Zhang <sonic.zhang@analog.com>
Signed-off-by: NMike Frysinger <vapier@gentoo.org>

arch/blackfin/kernel/traps.c

@@ -911,7 +911,7 @@ void show_stack(struct task_struct *task, unsigned long *stack)
 		frame_no = 0;
 
 		for (addr = (unsigned int *)((unsigned int)stack & ~0xF), i = 0;
-		     addr <= endstack; addr++, i++) {
+		     addr < endstack; addr++, i++) {
 
 			ret_addr = 0;
 			if (!j && i % 8 == 0)