Staging: speakup: devsynth.c: Remove explicit NULL comparison

Remove explicit NULL comparison and write it in its simpler form.
Replacement done with coccinelle:

@replace_rule@
expression e;
@@

-e == NULL
+ !e
Signed-off-by: Shraddha Barke <shraddha.6596@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/speakup/devsynth.c

@@ -22,7 +22,7 @@ static ssize_t speakup_file_write(struct file *fp, const char __user *buffer,
 	unsigned long flags;
 	u_char buf[256];
 
-	if (synth == NULL)
+	if (!synth)
 		return -ENODEV;
 	while (count > 0) {
 		bytes = min(count, sizeof(buf));
@@ -45,7 +45,7 @@ static ssize_t speakup_file_read(struct file *fp, char __user *buf,
 
 static int speakup_file_open(struct inode *ip, struct file *fp)
 {
-	if (synth == NULL)
+	if (!synth)
 		return -ENODEV;
 	if (xchg(&dev_opened, 1))
 		return -EBUSY;