[media] media: videobuf2: Move timestamp to vb2_buffer

Move timestamp from struct vb2_v4l2_buffer to struct vb2_buffer
for common use, and change its type to u64 in order to handling
y2038 problem. This patch also includes all device drivers' changes related to
this restructuring.

Signed-off-by: Junghak Sung <jh1009.sung@samsung.com>
Signed-off-by: Geunyoung Kim <nenggun.kim@samsung.com>
Acked-by: Seung-Woo Kim <sw0312.kim@samsung.com>
Acked-by: Inki Dae <inki.dae@samsung.com>
Signed-off-by: Hans Verkuil <hansverk@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>