[media] s5p-fimc: Avoid crash with null platform_data

In commit "s5p-fimc: Handle sub-device interdependencies using deferred.."
there was a check added for pdata->num_clients without first checking
pdata against NULL. This causes a crash when platform_data is not set,
which is a valid use case. Fix this regression by skipping the MIPI-CSIS
subdev registration also when pdata is null.
Reported-by: HeungJun Kim <riverful.kim@samsung.com>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/s5p-fimc/fimc-mdevice.c

@@ -371,6 +371,8 @@ static int fimc_md_register_platform_entities(struct fimc_md *fmd)
 	 * Check if there is any sensor on the MIPI-CSI2 bus and
 	 * if not skip the s5p-csis module loading.
 	 */
+	if (pdata == NULL)
+		return 0;
 	for (i = 0; i < pdata->num_clients; i++) {
 		if (pdata->isp_info[i].bus_type == FIMC_MIPI_CSI2) {
 			ret = 1;