ax88796: make pointer to platform data const

Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/ax88796.c

@@ -89,7 +89,7 @@ struct ax_device {
 	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;