Merge remote-tracking branch 'remotes/cohuck/tags/s390x-20180619' into staging

Merge remote-tracking branch 'remotes/cohuck/tags/s390x-20180619' into staging

- cleanup in virtio-ccw
- accommodate guests using vfio-ccw without specifying unlimited
  prefetch, but actually working fine
- add cpu model for the z14 Model ZR1
- add support for pxelinux.cfg-style network booting to the s390x
  firmware

# gpg: Signature made Tue 19 Jun 2018 10:33:06 BST
# gpg:                using RSA key DECF6B93C6F02FAF
# gpg: Good signature from "Cornelia Huck <conny@cornelia-huck.de>"
# gpg:                 aka "Cornelia Huck <huckc@linux.vnet.ibm.com>"
# gpg:                 aka "Cornelia Huck <cornelia.huck@de.ibm.com>"
# gpg:                 aka "Cornelia Huck <cohuck@kernel.org>"
# gpg:                 aka "Cornelia Huck <cohuck@redhat.com>"
# Primary key fingerprint: C3D0 D66D C362 4FF6 A8C0  18CE DECF 6B93 C6F0 2FAF

* remotes/cohuck/tags/s390x-20180619:
  pc-bios/s390-ccw: Update the s390-netboot.img binary
  pc-bios/s390-ccw: Optimize the s390-netboot.img for size
  pc-bios/s390-ccw/net: Try to load pxelinux.cfg file accoring to the UUID
  pc-bios/s390-ccw/net: Add support for pxelinux-style config files
  pc-bios/s390-ccw/net: Update code for the latest changes in SLOF
  roms: Update SLOF submodule to current status
  pc-bios/s390-ccw: define loadparm length
  s390x/cpumodels: add z14 Model ZR1
  s390x/ipl: Try to detect Linux vs non Linux for initial IPL PSW
  vfio-ccw: remove orb.c64 (64 bit data addresses) check
  vfio-ccw: add force unlimited prefetch property
  virtio-ccw: clean up notify

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