mmc: sh_mmcif: Check for null res pointer

If there is no suitable resource, platform_get_resource() will return
NULL.
Therefore in order to avoid the dereference of the NULL pointer, it
should be better to check the 'res'.

Signed-off-by: Jiasheng Jiang <jiasheng@iscas.ac.cn>
Cc: stable@vger.kernel.org # v5.16+
Link: https://lore.kernel.org/r/20220119120006.1426964-1-jiasheng@iscas.ac.cn
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

Author: JiangJias

drivers/mmc/host/sh_mmcif.c

@@ -405,6 +405,9 @@ static int sh_mmcif_dma_slave_config(struct sh_mmcif_host *host,
 	struct dma_slave_config cfg = { 0, };
 
 	res = platform_get_resource(host->pd, IORESOURCE_MEM, 0);
+	if (!res)
+		return -EINVAL;
+
 	cfg.direction = direction;
 
 	if (direction == DMA_DEV_TO_MEM) {