Merge remote-tracking branch 'remotes/cohuck/tags/s390x-20160614' into staging

More s390x patches, this time mostly dealing with channel I/O:
Bugfixes and cleanups, and dequeue pending interrupts after
machine checks.

# gpg: Signature made Tue 14 Jun 2016 13:09:43 BST
# gpg:                using RSA key 0xDECF6B93C6F02FAF
# gpg: Good signature from "Cornelia Huck <huckc@linux.vnet.ibm.com>"
# gpg:                 aka "Cornelia Huck <cornelia.huck@de.ibm.com>"
# Primary key fingerprint: C3D0 D66D C362 4FF6 A8C0  18CE DECF 6B93 C6F0 2FAF

* remotes/cohuck/tags/s390x-20160614:
  s390x/kvm: Fixup interrupt type for non-adapter I/O interrupts
  s390x: Limit s390-ccw machines to 248 CPUs
  virtio-ccw: Provide traces for indicator changes
  s390x/css: introduce property type for device ids
  s390x/css: clear IO irqs when generating IPI CRW
  s390x/kvm: add interface for clearing IO irqs
  linux-headers: update

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