libertas: treat firmware data as const

Signed-off-by: David Woodhouse <dwmw2@infradead.org>
diff --git a/drivers/net/wireless/libertas/if_sdio.c b/drivers/net/wireless/libertas/if_sdio.c
index 51f664b..3dd537b 100644
--- a/drivers/net/wireless/libertas/if_sdio.c
+++ b/drivers/net/wireless/libertas/if_sdio.c
@@ -392,7 +392,7 @@
 	unsigned long timeout;
 	u8 *chunk_buffer;
 	u32 chunk_size;
-	u8 *firmware;
+	const u8 *firmware;
 	size_t size;
 
 	lbs_deb_enter(LBS_DEB_SDIO);
@@ -508,7 +508,7 @@
 	unsigned long timeout;
 	u8 *chunk_buffer;
 	u32 chunk_size;
-	u8 *firmware;
+	const u8 *firmware;
 	size_t size, req_size;
 
 	lbs_deb_enter(LBS_DEB_SDIO);