Merge remote-tracking branch 'cohuck/tags/s390x-3270-20170504' into staging

Merge remote-tracking branch 'cohuck/tags/s390x-3270-20170504' into staging

Basic support for using channel-attached 3270 'green-screen'
devices via tn3270. Actual handling of the data stream is
delegated to x3270; more info at http://wiki.qemu.org/Features/3270

# gpg: Signature made Thu 04 May 2017 11:36:51 AM BST
# gpg:                using RSA key 0xDECF6B93C6F02FAF
# gpg: Good signature from "Cornelia Huck <conny@cornelia-huck.de>"
# gpg:                 aka "Cornelia Huck <cohuck@kernel.org>"
# gpg:                 aka "Cornelia Huck <cornelia.huck@de.ibm.com>"
# gpg:                 aka "Cornelia Huck <huckc@linux.vnet.ibm.com>"
# Primary key fingerprint: C3D0 D66D C362 4FF6 A8C0  18CE DECF 6B93 C6F0 2FAF

* cohuck/tags/s390x-3270-20170504:
  s390x/3270: Mark non-migratable and enable the device
  s390x/3270: Detect for continued presence of a 3270 client
  s390x/3270: Add the TCP socket events handler for 3270
  s390x/3270: 3270 data stream handling
  s390x/3270: Add emulated terminal3270 device
  s390x/3270: Add abstract emulated ccw-attached 3270 device
  s390x/css: Add an algorithm to find a free chpid
  chardev: Basic support for TN3270

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>