virtio: video: decoder: fix computed picture plane size
virtio: video: decoder: fix computed picture plane size

The picture buffer size was computed from the size of the visible
rectangle, which is potentially incorrect: if the origin of the visible
rectangle is not (0, 0) then the buffer is going to be larger.

Fix this by using the provided coded width and height, which correspond
to the actual size of the buffer and not just its visible area.

BUG=b:161774071
TEST=Android Youtube decodes properly on zork-arc-r.

Change-Id: I80e15248f41d6202190456d2ab61f8f50d3b6ebb
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3412457
Reviewed-by: Chih-Yu Huang <f815e8cb2f117b8947610323682cb280404b8de3@chromium.org>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Reviewed-by: Keiichi Watanabe <815e4e8f7c92a23424d7c3f51ead622bcedbc720@chromium.org>
Reviewed-by: David Staessens <a4557d4b9b905b8f9d5c87334b8d9f562e1ec119@chromium.org>
Commit-Queue: Alexandre Courbot <301cd6a3ea50a894b4b51e385c5eb12b9a4ffc0c@chromium.org>

google/crosvm,google/crosvm,google/crosvm,google/crosvm