tty: remove unnecessary export of proc_clear_tty

All of the users of proc_clear_tty are compiled into the kernel so exporting
this symbol appears gratuitous.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/char/tty_io.c

@@ -3834,7 +3834,6 @@ void proc_clear_tty(struct task_struct *p)
 	p->signal->tty = NULL;
 	spin_unlock_irq(&p->sighand->siglock);
 }
-EXPORT_SYMBOL(proc_clear_tty);
 
 static struct pid *__proc_set_tty(struct task_struct *tsk, struct tty_struct *tty)
 {