n_hdlc: remove unneeded ifdef

TTY_NO_WRITE_SPLIT is (always) defined in linux/tty.h, so no need to
check for it.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20200219084118.26491-18-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/n_hdlc.c

@@ -244,10 +244,8 @@ static int n_hdlc_tty_open (struct tty_struct *tty)
 	tty->disc_data = n_hdlc;
 	tty->receive_room = 65536;
 
-#if defined(TTY_NO_WRITE_SPLIT)
 	/* change tty_io write() to not split large writes into 8K chunks */
 	set_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
-#endif
 
 	/* flush receive data from driver */
 	tty_driver_flush_buffer(tty);