virtio, vhost, pc fixes for 2.4

The only notable thing here is vhost-user multiqueue
revert. We'll work on making it stable in 2.5,
reverting now means we won't have to maintain
bug for bug compability forever.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

# gpg: Signature made Mon Jul 20 12:24:00 2015 BST using RSA key ID D28D5469
# gpg: Good signature from "Michael S. Tsirkin <mst@kernel.org>"
# gpg:                 aka "Michael S. Tsirkin <mst@redhat.com>"

* remotes/mst/tags/for_upstream:
  virtio-net: remove virtio queues if the guest doesn't support multiqueue
  virtio-net: Flush incoming queues when DRIVER_OK is being set
  pci_add_capability: remove duplicate comments
  virtio-net: unbreak any layout
  Revert "vhost-user: add multi queue support"
  ich9: fix skipped vmstate_memhp_state subsection

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>