ax88796: make pointer to platform data const

Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
diff --git a/drivers/net/ax88796.c b/drivers/net/ax88796.c
index 782d73e..fd289e5 100644
--- a/drivers/net/ax88796.c
+++ b/drivers/net/ax88796.c
@@ -89,7 +89,7 @@
 	void __iomem *map2;
 	struct resource *mem;
 	struct resource *mem2;
-	struct ax_plat_data *plat;
+	const struct ax_plat_data *plat;
 
 	unsigned char running;
 	unsigned char resume_open;