tty: Kill TTY_FLIPBUF_SIZE

This legacy define from the old buffer code is now only used in a single
power pc driver than doesn't compile anyway.

Signed-off-by: Alan Cox <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

include/linux/tty.h

···
  */
 #define __DISABLED_CHAR '\0'
 
-/*
- * This is the flip buffer used for the tty driver.  The buffer is
- * located in the tty structure, and is used as a high speed interface
- * between the tty driver and the tty line discipline.
- */
-#define TTY_FLIPBUF_SIZE 512
-
 struct tty_buffer {
 	struct tty_buffer *next;
 	char *char_buf_ptr;