media: led-class-flash: better handle NULL flash struct

The logic at V4L2 led core assumes that the flash struct
can be null. However, it doesn't check for null while
trying to set, causing some smatch  to warn:

	drivers/media/v4l2-core/v4l2-flash-led-class.c:210 v4l2_flash_s_ctrl() error: we previously assumed 'fled_cdev' could be null (see line 200)
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

include/linux/led-class-flash.h

@@ -121,6 +121,8 @@ extern void led_classdev_flash_unregister(struct led_classdev_flash *fled_cdev);
 static inline int led_set_flash_strobe(struct led_classdev_flash *fled_cdev,
 					bool state)
 {
+	if (!fled_cdev)
+		return -EINVAL;
 	return fled_cdev->ops->strobe_set(fled_cdev, state);
 }
 
@@ -136,6 +138,8 @@ static inline int led_set_flash_strobe(struct led_classdev_flash *fled_cdev,
 static inline int led_get_flash_strobe(struct led_classdev_flash *fled_cdev,
 					bool *state)
 {
+	if (!fled_cdev)
+		return -EINVAL;
 	if (fled_cdev->ops->strobe_get)
 		return fled_cdev->ops->strobe_get(fled_cdev, state);