greybus: bundle: use kstrdup() for state file

The kernfs code guarantees we'll get a NUL-terminated buffer.
Use kstrdup() rather than kzalloc() + memcpy() in state_store()
making it slightly clearer what we're doing.  This has the added
benefit of guaranteeing that the stored string has no NUL character
inside it.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/bundle.c

@@ -48,12 +48,10 @@ static ssize_t state_store(struct device *dev, struct device_attribute *attr,
 	struct gb_bundle *bundle = to_gb_bundle(dev);
 
 	kfree(bundle->state);
-	bundle->state = kzalloc(size + 1, GFP_KERNEL);
+	bundle->state = kstrdup(buf, GFP_KERNEL);
 	if (!bundle->state)
 		return -ENOMEM;
 
-	memcpy(bundle->state, buf, size);
-
 	/* Tell userspace that the file contents changed */
 	sysfs_notify(&bundle->dev.kobj, NULL, "state");