CHROMIUM: drivers: media: virtio: Only supply timestamp for input queues.

The virtio-video spec states:
  timestamp: ... For VIRTIO_VIDEO_QUEUE_TYPE_OUTPUT, the driver MUST set
  it to 0.

For compliance purposes, only set this value for input queues. The struct
is zero-initialized on allocation, so timestamp will be 0 otherwise.

BUG=b:239897269
TEST=v4l2r decoding tests from crosvm book and FFmpeg encoding tests
     (https://crrev.com/c/3836232

) passes.
TEST=tast arc.VideoDecodeAccel*_vm
TEST=tast arc.VideoEncodeAccel*_vm

Change-Id: Id19a352dfe036273699440ee9d053fd79700baef
Signed-off-by: Tatsuyuki Ishi <ishitatsuyuki@google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/3852533


Reviewed-by: Alexandre Courbot <acourbot@chromium.org>