CHROMIUM: drivers: media: virtio: do not call set_params during REQBUFS(0)

Do not call set_params during REQBUFS(0). If the count is zero, the
queue is freed and we should not do any further processing. Calling
set_params in this case is correctly identified by CrosVM as a mistake
and the following error is emitted:

[ERROR devices::virtio::video::decoder] parameter for input cannot be
changed once decoding started

BUG=b:161774071
TEST=emerge-brya sys-kernel/arcvm-kernel-ack-5_10

Signed-off-by: Daniel Almeida <daniel.almeida@collabora.com>
Signed-off-by: Alexandre Courbot <acourbot@chromium.org>

Change-Id: Icb5012df2a5e7085d3f8f84e86f7f59903803f07
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/4066822


Reviewed-by: Keiichi Watanabe <keiichiw@chromium.org>
Auto-Submit: Alexandre Courbot <acourbot@chromium.org>
Commit-Queue: Alexandre Courbot <acourbot@chromium.org>
Tested-by: Alexandre Courbot <acourbot@chromium.org>
Reviewed-by: Bartłomiej Grzesik <bgrzesik@google.com>
Signed-off-by: Slawomir Rosek <srosek@google.com>