ARM: cache-l2x0: add a const qualifier

This prepares *of_device_id.data becoming const. Without this change the
following warning would occur:

	arch/arm/mm/cache-l2x0.c: In function 'l2x0_of_init':
	arch/arm/mm/cache-l2x0.c:573:7: warning: assignment discards 'const' qualifier from pointer target type [enabled by default]

though.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

arch/arm/mm/cache-l2x0.c

@@ -554,7 +554,7 @@ static const struct of_device_id l2x0_ids[] __initconst = {
 int __init l2x0_of_init(u32 aux_val, u32 aux_mask)
 {
 	struct device_node *np;
-	struct l2x0_of_data *data;
+	const struct l2x0_of_data *data;
 	struct resource res;
 
 	np = of_find_matching_node(NULL, l2x0_ids);