[media] davinci: vpbe: fix check for s_dv_preset function pointer

fix check for s_dv_preset function pointer to be NULL.
return -EINVAL if function pointer is NULL.

Signed-off-by: Lad, Prabhakar <prabhakar.lad@ti.com>
Signed-off-by: Manjunath Hadli <manjunath.hadli@ti.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/davinci/vpbe_display.c

@@ -1083,7 +1083,7 @@ vpbe_display_s_dv_preset(struct file *file, void *priv,
 	}
 
 	/* Set the given standard in the encoder */
-	if (NULL != vpbe_dev->ops.s_dv_preset)
+	if (!vpbe_dev->ops.s_dv_preset)
 		return -EINVAL;
 
 	ret = vpbe_dev->ops.s_dv_preset(vpbe_dev, preset);