mmc: mxs: Constify platform_device_id

The platform_device_id is not modified by the driver and core uses it as
const.
Signed-off-by: NKrzysztof Kozlowski <k.kozlowski.k@gmail.com>
Signed-off-by: NUlf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/mxs-mmc.c

@@ -549,7 +549,7 @@ static const struct mmc_host_ops mxs_mmc_ops = {
 	.enable_sdio_irq = mxs_mmc_enable_sdio_irq,
 };
 
-static struct platform_device_id mxs_ssp_ids[] = {
+static const struct platform_device_id mxs_ssp_ids[] = {
 	{
 		.name = "imx23-mmc",
 		.driver_data = IMX23_SSP,