V4L/DVB (5842): ivtv: Add locking to ensure stream setup is atomic.

Starting an MPEG and VBI capture simultaneously caused errors in
the VBI setup: this setup was done twice when it should be done
only for the first stream that is opened.
Added a mutex to prevent this from happening.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
diff --git a/drivers/media/video/ivtv/ivtv-driver.h b/drivers/media/video/ivtv/ivtv-driver.h
index 48afd42..65ebdda 100644
--- a/drivers/media/video/ivtv/ivtv-driver.h
+++ b/drivers/media/video/ivtv/ivtv-driver.h
@@ -722,6 +722,7 @@
 	int search_pack_header;
 
 	spinlock_t dma_reg_lock; /* lock access to DMA engine registers */
+	struct mutex serialize_lock;  /* lock used to serialize starting streams */
 
 	/* User based DMA for OSD */
 	struct ivtv_user_dma udma;