CONFIG_UNIX98_PTY=n warning fix

diff -Nru a/drivers/char/tty_io.c b/drivers/char/tty_io.c
@@ -136,6 +136,7 @@
 extern int pty_limit;		/* Config limit on Unix98 ptys */
 static DEFINE_IDR(allocated_ptys);
 static DECLARE_MUTEX(allocated_ptys_lock);
+static int ptmx_open(struct inode *, struct file *);
 #endif
 
 extern void disable_early_printk(void);

@@ -147,7 +148,6 @@
 ssize_t redirected_tty_write(struct file *, const char __user *, size_t, loff_t *);
 static unsigned int tty_poll(struct file *, poll_table *);
 static int tty_open(struct inode *, struct file *);
-static int ptmx_open(struct inode *, struct file *);
 static int tty_release(struct inode *, struct file *);
 int tty_ioctl(struct inode * inode, struct file * file,
 	      unsigned int cmd, unsigned long arg);