mei: mei_release: drop redundant check if cb is NULL

mei_io_cb_free follows kfree design and check for NULL internally
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/mei/main.c

@@ -165,10 +165,7 @@ static int mei_release(struct inode *inode, struct file *file)
 
 	file->private_data = NULL;
 
-	if (cb) {
-		mei_io_cb_free(cb);
-		cb = NULL;
-	}
+	mei_io_cb_free(cb);
 
 	kfree(cl);
 out: