V4L/DVB (5702): Fix Kconfig items to avoid linkedition errors

The recent changes on Kconfig broke compilation when VIDEO_DEV is compiled
as module. On some cases, drivers like VIDEO_BUF are compiled with 'y' option
instead of 'm':

...

Thanks to: Toralf Forster <toralf.foerster@gmx.de> for pointing this issue.
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
diff --git a/drivers/media/common/Kconfig b/drivers/media/common/Kconfig
index c120114..5c63c8e 100644
--- a/drivers/media/common/Kconfig
+++ b/drivers/media/common/Kconfig
@@ -4,5 +4,6 @@
 
 config VIDEO_SAA7146_VV
 	tristate
+	depends on VIDEO_DEV
 	select VIDEO_BUF
 	select VIDEO_SAA7146