s390x/kvm/migration/cpumodel: fixes, enhancements and cleanups

- add a network boot rom for s390 (Thomas Huth)
- migration of storage attributes like the CMMA used/unused state
- PCI related enhancements - full support for aen, ais and zpci
- migration support for css with vmstates (Halil Pasic)
- cpu model enhancements for cpu features
- guarded storage support

# gpg: Signature made Fri 14 Jul 2017 11:33:04 BST
# gpg:                using RSA key 0x117BBC80B5A61C7C
# gpg: Good signature from "Christian Borntraeger (IBM) <borntraeger@de.ibm.com>"
# Primary key fingerprint: F922 9381 A334 08F9 DBAB  FBCA 117B BC80 B5A6 1C7C

* remotes/borntraeger/tags/s390x-20170714: (40 commits)
  s390x/gdb: add gs registers
  s390x/arch_dump: also dump guarded storage control block
  s390x/kvm: enable guarded storage
  s390x/kvm: Enable KSS facility for nested virtualization
  s390x/cpumodel: add esop/esop2 to z12 model
  s390x/cpumodel: we are always in zarchitecture mode
  s390x/cpumodel: wire up new hardware features
  s390x/flic: migrate ais states
  s390x/cpumodel: add zpci, aen and ais facilities
  s390x: initialize cpu firstly
  pc-bios/s390: rebuild s390-ccw.img
  pc-bios/s390: add s390-netboot.img
  pc-bios/s390-ccw: Link libnet into the netboot image and do the TFTP load
  pc-bios/s390-ccw: Add virtio-net driver code
  pc-bios/s390-ccw: Add core files for the network bootloading program
  roms/SLOF: Update submodule to latest status
  pc-bios/s390-ccw: Add code for virtio feature negotiation
  pc-bios/s390-ccw: Remove unused structs from virtio.h
  pc-bios/s390-ccw: Move byteswap functions to a separate header
  pc-bios/s390-ccw: Add a write() function for stdio
  ...

Conflicts:
	target/s390x/kvm.c
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>