staging: speakup: Comparison to NULL.

Fix coding style issues, detected by checkpatch.pl "CHECK: Comparison to
NULL could be written !tty->ops->write"
Signed-off-by: Bhagyashri Dighole <digholebhagyashri@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/speakup/spk_ttyio.c

@@ -47,7 +47,7 @@ static int spk_ttyio_ldisc_open(struct tty_struct *tty)
 {
 	struct spk_ldisc_data *ldisc_data;
 
-	if (tty->ops->write == NULL)
+	if (!tty->ops->write)
 		return -EOPNOTSUPP;
 	speakup_tty = tty;