ALSA: 6fire: use NULL instead of 0 for pointer assignment

Signed-off-by: Daniel Mack <zonque@gmail.com>
Cc: Torsten Schenk <torsten.schenk@zoho.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/6fire/firmware.c

@@ -209,7 +209,7 @@ static int usb6fire_fw_ezusb_upload(
 	int ret;
 	u8 data;
 	struct usb_device *device = interface_to_usbdev(intf);
-	const struct firmware *fw = 0;
+	const struct firmware *fw = NULL;
 	struct ihex_record *rec = kmalloc(sizeof(struct ihex_record),
 			GFP_KERNEL);