input: add vhost-user-input, virtio-input fixes.

# gpg: Signature made Mon 13 May 2019 07:52:39 BST
# gpg:                using RSA key 4CB6D8EED3E87138
# gpg: Good signature from "Gerd Hoffmann (work) <kraxel@redhat.com>" [full]
# gpg:                 aka "Gerd Hoffmann <gerd@kraxel.org>" [full]
# gpg:                 aka "Gerd Hoffmann (private) <kraxel@gmail.com>" [full]
# Primary key fingerprint: A032 8CFF B93A 17A7 9901  FE7D 4CB6 D8EE D3E8 7138

* remotes/kraxel/tags/input-20190513-v2-pull-request:
  virtio-input: fix Kconfig dependency and Makefile
  virtio-input-host-pci: cleanup types
  util: simplify unix_listen()
  Add vhost-user-input-pci
  Add vhost-user-backend
  libvhost-user: add PROTOCOL_F_CONFIG if {set, get}_config
  libvhost-user: fix -Waddress-of-packed-member

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