Merge remote-tracking branch 'remotes/dgibson/tags/ppc-for-3.0-20180716' into staging

ppc patch queue 2018-07-16

Here's my first hard freeze pull request for qemu-3.0.  This contains
an assortment of bugfixes. Several are for regressions, others are for
bugs that I think are significant enough to address during hard freeze.

# gpg: Signature made Mon 16 Jul 2018 09:28:37 BST
# gpg:                using RSA key 6C38CACA20D9B392
# gpg: Good signature from "David Gibson <david@gibson.dropbear.id.au>"
# gpg:                 aka "David Gibson (Red Hat) <dgibson@redhat.com>"
# gpg:                 aka "David Gibson (ozlabs.org) <dgibson@ozlabs.org>"
# gpg:                 aka "David Gibson (kernel.org) <dwg@kernel.org>"
# Primary key fingerprint: 75F4 6586 AE61 A66C C44E  87DC 6C38 CACA 20D9 B392

* remotes/dgibson/tags/ppc-for-3.0-20180716:
  sm501: Fix warning about unreachable code
  sam460ex: Correct use after free error
  etsec: fix IRQ (un)masking
  ppc/xics: fix ICP reset path
  spapr: Correct inverted test in spapr_pc_dimm_node()
  sm501: Update screen on frame buffer address change

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