V4L/DVB (4706): Do not enable VIDEO_V4L2 unconditionally

The VIDEO_V4L2 config setting is enabled unconditionally, even for 
configurations with no support for this subsystem whatsoever.  The 
following patch adds the necessary dependency.
Signed-off-by: NMaciej W. Rozycki <macro@linux-mips.org>
Signed-off-by: NMauro Carvalho Chehab <mchehab@infradead.org>

drivers/media/Kconfig

@@ -54,6 +54,7 @@ config VIDEO_V4L1_COMPAT
 
 config VIDEO_V4L2
 	bool
+	depends on VIDEO_DEV
 	default y
 
 source "drivers/media/video/Kconfig"