virtio_console: break out of buf poll on remove

[ Upstream commit 0e7174b9d5877130fec41fb4a16e0c2ee4958d44 ]

A common pattern for device reset is currently:
vdev->config->reset(vdev);
.. cleanup ..

reset prevents new interrupts from arriving and waits for interrupt
handlers to finish.

However if - as is common - the handler queues a work request which is
flushed during the cleanup stage, we have code adding buffers / trying
to get buffers while device is reset. Not good.

This was reproduced by running
	modprobe virtio_console
	modprobe -r virtio_console
in a loop.

Fix this up by calling virtio_break_device + flush before reset.

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1786239


Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>