qtest: Add set_irq_in command to set IRQ/GPIO level

qtest: Add set_irq_in command to set IRQ/GPIO level

Adds a new qtest command "set_irq_in" which allows
to set qemu gpio lines to a given level.

Based on https://lists.gnu.org/archive/html/qemu-devel/2012-12/msg02363.html
which never got merged.

Signed-off-by: Steffen Görtz <contrib@steffen-goertz.de>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Laurent Vivier <lvivier@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20190103091119.9367-2-stefanha@redhat.com
Originally-by: Matthew Ogilvie <mmogilvi_qemu@miniinfo.net>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Laurent Vivier <lvivier@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>