V4L/DVB (6308): V4L: zc0301, remove bad usage of ERESTARTSYS

zc0301, remove bad usage of ERESTARTSYS

down_read_trylock can't be interrupted and so ERESTARTSYS would reach
userspace, which is not permitted. Change it to EAGAIN
Signed-off-by: NJiri Slaby <jirislaby@gmail.com>
Acked-by: NLuca Risolia <luca.risolia@studio.unibo.it>
Signed-off-by: NMauro Carvalho Chehab <mchehab@infradead.org>

drivers/media/video/zc0301/zc0301_core.c

@@ -655,7 +655,7 @@ static int zc0301_open(struct inode* inode, struct file* filp)
 	int err = 0;
 
 	if (!down_read_trylock(&zc0301_dev_lock))
-		return -ERESTARTSYS;
+		return -EAGAIN;
 
 	cam = video_get_drvdata(video_devdata(filp));