tty: drop termiox user definitions

As was concluded in a follow-up discussion of commit e0efb316 (tty:
Remove dead termiox code) [1], termiox ioctls never worked, so there is
barely anyone using this interface. We can safely remove the user
definitions for this never adopted interface.

[1] https://lore.kernel.org/lkml/c1c9fc04-02eb-2260-195b-44c357f057c0@kernel.org/t/#uSigned-off-by: NJiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210105120239.28031-12-jslaby@suse.czSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

include/uapi/linux/termios.h

@@ -5,19 +5,4 @@
 #include <linux/types.h>
 #include <asm/termios.h>
 
-#define NFF	5
-
-struct termiox
-{
-	__u16	x_hflag;
-	__u16	x_cflag;
-	__u16	x_rflag[NFF];
-	__u16	x_sflag;
-};
-
-#define	RTSXOFF		0x0001		/* RTS flow control on input */
-#define	CTSXON		0x0002		/* CTS flow control on output */
-#define	DTRXOFF		0x0004		/* DTR flow control on input */
-#define DSRXON		0x0008		/* DCD flow control on output */
-
 #endif