rt2x00: fix rt2x00usb_register_multiwrite() arguments

Add const to 'value' argument of rt2x00usb_register_multiwrite()
(all arguments match rt2x00pci_register_multiwrite() ones now).
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Acked-by: Ivo van Doorn <IvDoorn@gmail.com>
Acked-by: Gertjan van Wingerde <gwingerde@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/rt2x00/rt2800usb.h

@@ -40,7 +40,7 @@ struct rt2800_ops {
 				   void *value, const u32 length);
 	void (*register_multiwrite)(struct rt2x00_dev *rt2x00dev,
 				    const unsigned int offset,
-				    void *value, const u32 length);
+				    const void *value, const u32 length);
 
 	int (*regbusy_read)(struct rt2x00_dev *rt2x00dev,
 			    const unsigned int offset,

drivers/net/wireless/rt2x00/rt2x00usb.h

@@ -341,11 +341,12 @@ static inline void rt2x00usb_register_write_lock(struct rt2x00_dev *rt2x00dev,
  */
 static inline void rt2x00usb_register_multiwrite(struct rt2x00_dev *rt2x00dev,
 						 const unsigned int offset,
-					       void *value, const u32 length)
+						 const void *value,
+						 const u32 length)
 {
 	rt2x00usb_vendor_request_buff(rt2x00dev, USB_MULTI_WRITE,
 				      USB_VENDOR_REQUEST_OUT, offset,
-				      value, length,
+				      (void *)value, length,
 				      REGISTER_TIMEOUT32(length));
 }