cxacru: treat firmware data as const

Signed-off-by: David Woodhouse <dwmw2@infradead.org>

drivers/usb/atm/cxacru.c

@@ -820,7 +820,7 @@ reschedule:
 }
 
 static int cxacru_fw(struct usb_device *usb_dev, enum cxacru_fw_request fw,
-		     u8 code1, u8 code2, u32 addr, u8 *data, int size)
+		     u8 code1, u8 code2, u32 addr, const u8 *data, int size)
 {
 	int ret;
 	u8 *buf;