mmc: exynos_dw_mmc: add the error control for checking index

PERIPH_ID_SDMMC4(131) is not continous value with PERIPH_ID_SDMMC0(75).
If there is no 'index' property in fdt, then dev_index should be
assigned to dev_id(Peripheral ID).
At this time, dev_index should be "56". It means Exynos SoC has "56"
numbers of DWMMC IP. To prevent this behavior, it needs to check the
maximum device index.

Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>

drivers/mmc/exynos_dw_mmc.c

@@ -160,6 +160,11 @@ static int exynos_dwmci_get_config(const void *blob, int node,
 	if (host->dev_index == host->dev_id)
 		host->dev_index = host->dev_id - PERIPH_ID_SDMMC0;
 
+	if (host->dev_index > 4) {
+		printf("DWMMC%d: Can't get the dev index\n", host->dev_index);
+		return -EINVAL;
+	}
+
 	/* Get the bus width from the device node */
 	host->buswidth = fdtdec_get_int(blob, node, "samsung,bus-width", 0);
 	if (host->buswidth <= 0) {