tty: Remove dead tty_write_flush() declaration and macro

tty_write_flush() has no definition and the TTY_WRITE_FLUSH() macro
is never invoked; remove.
Signed-off-by: NPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

include/linux/tty.h

@@ -345,8 +345,6 @@ struct tty_file_private {
 #define TTY_HUPPED 		18	/* Post driver->hangup() */
 #define TTY_LDISC_HALTED	22	/* Line discipline is halted */
 
-#define TTY_WRITE_FLUSH(tty) tty_write_flush((tty))
-
 /* Values for tty->flow_change */
 #define TTY_THROTTLE_SAFE 1
 #define TTY_UNTHROTTLE_SAFE 2
@@ -395,8 +393,6 @@ static inline int __init tty_init(void)
 { return 0; }
 #endif
 
-extern void tty_write_flush(struct tty_struct *);
-
 extern struct ktermios tty_std_termios;
 
 extern int vcs_init(void);