ALSA: snd-usb-caiaq: Fix NULL dereference in input.c

There was a case where a newly-registered input device could be opened before
a necessary variable in the device structure was set. When code tried to use
the variable in the URB reply callback, it would cause an Oops.

This fix sets the aforementioned variable before calling input_register_device.
Signed-off-by: William Light <wrl@illest.net>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/caiaq/input.c

@@ -664,15 +664,17 @@ int snd_usb_caiaq_input_init(struct snd_usb_caiaqdev *dev)
 	for (i = 0; i < input->keycodemax; i++)
 		__set_bit(dev->keycode[i], input->keybit);
 
+	dev->input_dev = input;
+
 	ret = input_register_device(input);
 	if (ret < 0)
 		goto exit_free_idev;
 
-	dev->input_dev = input;
 	return 0;
 
 exit_free_idev:
 	input_free_device(input);
+	dev->input_dev = NULL;
 	return ret;
 }