Merge remote-tracking branch 'remotes/alistair/tags/pull-riscv-pullreq-20180905'...

A misc collection of RISC-V related patches for 3.1.

# gpg: Signature made Wed 05 Sep 2018 23:06:55 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-pullreq-20180905:
  riscv: remove define cpu_init()
  hw/riscv/spike: Set the soc device tree node as a simple-bus
  hw/riscv/virtio: Set the soc device tree node as a simple-bus
  target/riscv: call gen_goto_tb on DISAS_TOO_MANY
  target/riscv: optimize indirect branches
  target/riscv: optimize cross-page direct jumps in softmmu
  RISC-V: Simplify riscv_cpu_local_irqs_pending
  RISC-V: Use atomic_cmpxchg to update PLIC bitmaps
  RISC-V: Improve page table walker spec compliance
  RISC-V: Update address bits to support sv39 and sv48

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