device: Keep DV-timing Hz

(cherry picked from commit 17a448223c0dd1cf420ba9a79232f433ff11c4b5)
Signed-off-by: Maxim Devaev <mdevaev@gmail.com>

src/libs/device.h

@@ -80,6 +80,7 @@ typedef struct {
 	unsigned			height;
 	unsigned			format;
 	unsigned			stride;
+	float				hz;
 	unsigned			hw_fps;
 	unsigned			jpeg_quality;
 	size_t				raw_size;