drm/sprd: check the platform_get_resource() return value

platform_get_resource() may fail and return NULL, so check it's value
before using it.

Reported-by: Zou Wei <zou_wei@huawei.com>
Signed-off-by: Kevin Tang <kevin3.tang@gmail.com>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://lore.kernel.org/all/20220117084156.9338-1-kevin3.tang@gmail.com

v1 -> v2:
- new patch

drivers/gpu/drm/sprd/sprd_dpu.c

@@ -790,6 +790,11 @@ static int sprd_dpu_context_init(struct sprd_dpu *dpu,
 	int ret;
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res) {
+		dev_err(dev, "failed to get I/O resource\n");
+		return -EINVAL;
+	}
+
 	ctx->base = devm_ioremap(dev, res->start, resource_size(res));
 	if (!ctx->base) {
 		dev_err(dev, "failed to map dpu registers\n");

drivers/gpu/drm/sprd/sprd_dsi.c

@@ -907,6 +907,11 @@ static int sprd_dsi_context_init(struct sprd_dsi *dsi,
 	struct resource *res;
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res) {
+		dev_err(dev, "failed to get I/O resource\n");
+		return -EINVAL;
+	}
+
 	ctx->base = devm_ioremap(dev, res->start, resource_size(res));
 	if (!ctx->base) {
 		drm_err(dsi->drm, "failed to map dsi host registers\n");