tty: Remove defunct serial_console_init() declaration

serial_console_init() is not defined by the tty core; remove
declaration.

Note that the powerpc arch boot code contains a serial_console_init()
declaration in arch/powerpc/boot/ops.h which is restricted to
the powerpc arch boot.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

include/linux/tty.h

@@ -617,10 +617,6 @@ extern int n_tty_ioctl_helper(struct tty_struct *tty, struct file *file,
 extern long n_tty_compat_ioctl_helper(struct tty_struct *tty, struct file *file,
 		       unsigned int cmd, unsigned long arg);
 
-/* serial.c */
-
-extern void serial_console_init(void);
-
 /* vt.c */
 
 extern int vt_ioctl(struct tty_struct *tty,