devices: virtio: Fix the vhost worker to set actual queue size to the vhost device
devices: virtio: Fix the vhost worker to set actual queue size to the vhost device

Vhost worker uses the maximum queue size the host offers when setting a
queue size to the vhost device, which leads inappropriate behavior when
a guest preapares a virtqueue whose size is smaller than the maximum
size.
Fix the vhost worker to set the actual queue size to the vhost device.

BUG=b:235857465
TEST=`cargo build`
TEST=`./tools/run_tests`
TEST=host and guest can communicate via vhost-vsock

Change-Id: I99af745788c347ca2770b979252f8ea8dde34462
Reviewed-on: https://chromium-review.googlesource.com/c/crosvm/crosvm/+/3946422
Commit-Queue: Ryuichiro Chiba <726e8d6335a479f18bac699535a964882dab2202@chromium.org>
Reviewed-by: Keiichi Watanabe <815e4e8f7c92a23424d7c3f51ead622bcedbc720@chromium.org>
Reviewed-by: Takaya Saeki <b41986321ffdf64f9ab5b24fec89eb23749dcec8@chromium.org>

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