Merge remote-tracking branch 'remotes/alistair/tags/pull-riscv-pull-20180719' into...

riscv: Fix introspection problems

This is based on Thomas's work fixing introspection problems [1] and
applied to the RISC-V port.

1: https://lists.gnu.org/archive/html/qemu-devel/2018-07/msg03261.html

# gpg: Signature made Thu 19 Jul 2018 17:06:07 BST
# gpg:                using RSA key 21E10D29DF977054
# gpg: Good signature from "Alistair Francis <alistair@alistair23.me>"
# gpg: WARNING: This key is not certified with sufficiently trusted signatures!
# gpg:          It is not certain that the signature belongs to the owner.
# Primary key fingerprint: F6C4 AC46 D493 4868 D3B8  CE8F 21E1 0D29 DF97 7054

* remotes/alistair/tags/pull-riscv-pull-20180719:
  spike: Fix crash when introspecting the device
  riscv_hart: Fix crash when introspecting the device
  virt: Fix crash when introspecting the device
  sifive_u: Fix crash when introspecting the device
  sifive_e: Fix crash when introspecting the device

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