vhost: fix virtio ready flag check

vhost: fix virtio ready flag check

Before checking whether the device is ready is done
a check on whether the RUNNING flag is set. Then the
READY flag is set if virtio_is_ready() returns true.

While it seems to not cause any issue, it makes more
sense to check whether the READY flag is set and not
the RUNNING one.

Fixes: c0674b1bc898 ("vhost: move the device ready check at proper place")
Cc: stable@dpdk.org
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Reviewed-by: Chenbo Xia <chenbo.xia@intel.com>