tests/qtest: enable tests for virtio-gpio

tests/qtest: enable tests for virtio-gpio

We don't have a virtio-gpio implementation in QEMU and only
support a vhost-user backend. The QEMU side of the code is minimal so
it should be enough to instantiate the device and pass some vhost-user
messages over the control socket. To do this we hook into the existing
vhost-user-test code and just add the bits required for gpio.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Eric Auger <eric.auger@redhat.com>
Message-Id: <20220408155704.2777166-1-alex.bennee@linaro.org>

Message-Id: <20220802095010.3330793-23-alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>