mfd: wm8400-core: Make mfd_cell array const

mfd_add_devices() expects array of struct mfd_cell to be const.
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Acked-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/mfd/wm8400-core.c

@@ -64,7 +64,7 @@ EXPORT_SYMBOL_GPL(wm8400_block_read);
 
 static int wm8400_register_codec(struct wm8400 *wm8400)
 {
-	struct mfd_cell cell = {
+	const struct mfd_cell cell = {
 		.name = "wm8400-codec",
 		.platform_data = wm8400,
 		.pdata_size = sizeof(*wm8400),