Merge remote-tracking branch 'remotes/alistair/tags/pull-riscv-to-apply-20200429...

RISC-V pull request for 5.1

This is the first pull request for the 5.1 development period. It
contains all of the patches that were sent during the 5.0 timeframe.

This is an assortment of fixes for RISC-V, including fixes for the
Hypervisor extension, the Spike machine and an update to OpenSBI.

# gpg: Signature made Wed 29 Apr 2020 21:17:17 BST
# gpg:                using RSA key F6C4AC46D4934868D3B8CE8F21E10D29DF977054
# gpg: Good signature from "Alistair Francis <alistair@alistair23.me>" [full]
# Primary key fingerprint: F6C4 AC46 D493 4868 D3B8  CE8F 21E1 0D29 DF97 7054

* remotes/alistair/tags/pull-riscv-to-apply-20200429-2:
  hw/riscv/spike: Allow more than one CPUs
  hw/riscv/spike: Allow loading firmware separately using -bios option
  hw/riscv: Add optional symbol callback ptr to riscv_load_firmware()
  roms: opensbi: Upgrade from v0.6 to v0.7
  linux-user/riscv: fix up struct target_ucontext definition
  target/riscv: Add a sifive-e34 cpu type
  riscv: sifive_e: Support changing CPU type
  hw/riscv: Generate correct "mmu-type" for 32-bit machines
  riscv: Fix Stage2 SV32 page table walk
  riscv: AND stage-1 and stage-2 protection flags
  riscv: Don't use stage-2 PTE lookup protection flags
  riscv/sifive_u: Add a serial property to the sifive_u machine
  riscv/sifive_u: Add a serial property to the sifive_u SoC
  riscv/sifive_u: Fix up file ordering

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