Merge remote-tracking branch 'remotes/cohuck/tags/s390x-20180514' into staging

Merge remote-tracking branch 'remotes/cohuck/tags/s390x-20180514' into staging

Some s390x fixes/cleanups, mainly in the reset area and build fixes
for recent compilers (GCC 8 and clang 6.0.0).

# gpg: Signature made Mon 14 May 2018 16:32:20 BST
# gpg:                using RSA key DECF6B93C6F02FAF
# gpg: Good signature from "Cornelia Huck <[email protected]>"
# gpg:                 aka "Cornelia Huck <[email protected]>"
# gpg:                 aka "Cornelia Huck <[email protected]>"
# gpg:                 aka "Cornelia Huck <[email protected]>"
# gpg:                 aka "Cornelia Huck <[email protected]>"
# Primary key fingerprint: C3D0 D66D C362 4FF6 A8C0  18CE DECF 6B93 C6F0 2FAF

* remotes/cohuck/tags/s390x-20180514:
  target/s390x: Fix brace Werror with clang 6.0.0
  s390x: refactor reset/reipl handling
  s390x/ccw: make sure all ccw devices are properly reset
  virtio-ccw: common reset handler
  pc-bios/s390-ccw: struct tpi_info must be declared as aligned(4)
  s390x/css: disabled subchannels cannot be status pending

Signed-off-by: Peter Maydell <[email protected]>