printk: when dumping regs, show the stack, not thread_info

We currently show:

  task: <current> ti: <current_thread_info()> task.ti: <task_thread_info(current)>"

"ti" and "task.ti" are redundant, and neither is actually what we
want to show, which the the base of the thread stack.  Change the
display to show the stack pointer explicitly.

Link: http://lkml.kernel.org/r/543ac5bd66ff94000a57a02e11af7239571a3055.1468523549.git.luto@kernel.org
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: amluto

kernel/printk/printk.c

@@ -3177,9 +3177,8 @@ void show_regs_print_info(const char *log_lvl)
 {
 	dump_stack_print_info(log_lvl);
 
-	printk("%stask: %p ti: %p task.ti: %p\n",
-	       log_lvl, current, current_thread_info(),
-	       task_thread_info(current));
+	printk("%stask: %p task.stack: %p\n",
+	       log_lvl, current, task_stack_page(current));
 }
 
 #endif