rt2x00: treat firmware data as const

Signed-off-by: David Woodhouse <dwmw2@infradead.org>
diff --git a/drivers/net/wireless/rt2x00/rt2x00pci.h b/drivers/net/wireless/rt2x00/rt2x00pci.h
index 9d1cdb9..b41967e 100644
--- a/drivers/net/wireless/rt2x00/rt2x00pci.h
+++ b/drivers/net/wireless/rt2x00/rt2x00pci.h
@@ -82,7 +82,7 @@
 static inline void
 rt2x00pci_register_multiwrite(struct rt2x00_dev *rt2x00dev,
 			      const unsigned long offset,
-			      void *value, const u16 length)
+			      const void *value, const u16 length)
 {
 	memcpy_toio(rt2x00dev->csr.base + offset, value, length);
 }