If a pmem device is in a bad status, the driver side could wait for
host ack forever in virtio_pmem_flush(), causing the system to hang.

So add a status check in the beginning of virtio_pmem_flush() to return
early if the device is not activated.
Signed-off-by: Philip Chen <philipchen@chromium.org>
Message-Id: <20240826215313.2673566-1-philipchen@chromium.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com