Merge remote-tracking branch 'remotes/alistair/tags/pull-riscv-to-apply-20200821-1' into staging

The first RISC-V PR for the 5.2 window.

This includes:
 - NaNBox fixes
 - Vector extension improvements
 - a L2 cache controller
 - PMP fixes
 - Upgrade to OpenSBI v0.8 and the generic platform
 - Fixes for the Ibex PLIC

# gpg: Signature made Sat 22 Aug 2020 06:38:18 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-20200821-1:
  hw/intc: ibex_plic: Honour source priorities
  hw/intc: ibex_plic: Don't allow repeat interrupts on claimed lines
  hw/intc: ibex_plic: Update the pending irqs
  target/riscv: Change the TLB page size depends on PMP entries.
  target/riscv: Fix the translation of physical address
  gitlab-ci/opensbi: Update GitLab CI to build generic platform
  hw/riscv: spike: Change the default bios to use generic platform image
  hw/riscv: Use pre-built bios image of generic platform for virt & sifive_u
  roms/Makefile: Build the generic platform for RISC-V OpenSBI firmware
  roms/opensbi: Upgrade from v0.7 to v0.8
  configure: Create symbolic links for pc-bios/*.elf files
  riscv: Fix bug in setting pmpcfg CSR for RISCV64
  hw/riscv: sifive_u: Add a dummy L2 cache controller device
  target/riscv: check before allocating TCG temps
  target/riscv: Clean up fmv.w.x
  target/riscv: Check nanboxed inputs in trans_rvf.inc.c
  target/riscv: Check nanboxed inputs to fp helpers
  target/riscv: Generate nanboxed results from trans_rvf.inc.c
  target/riscv: Generalize gen_nanbox_fpr to gen_nanbox_s
  target/riscv: Generate nanboxed results from fp helpers

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