Merge remote-tracking branch 'remotes/alistair/tags/pull-riscv-to-apply-20210322...

Merge remote-tracking branch 'remotes/alistair/tags/pull-riscv-to-apply-20210322-2' into staging

RISC-V PR for 6.0

This PR includes:
 - Fix for vector CSR access
 - Improvements to the Ibex UART device
 - PMP improvements and bug fixes
 - Hypervisor extension bug fixes
 - ramfb support for the virt machine
 - Fast read support for SST flash
 - Improvements to the microchip_pfsoc machine

# gpg: Signature made Tue 23 Mar 2021 01:56:53 GMT
# 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-20210322-2:
  target/riscv: Prevent lost illegal instruction exceptions
  docs/system: riscv: Add documentation for 'microchip-icicle-kit' machine
  hw/riscv: microchip_pfsoc: Map EMMC/SD mux register
  hw/block: m25p80: Support fast read for SST flashes
  target/riscv: Add proper two-stage lookup exception detection
  target/riscv: Fix read and write accesses to vsip and vsie
  hw/riscv: allow ramfb on virt
  hw/riscv: Add fw_cfg support to virt
  target/riscv: Use background registers also for MSTATUS_MPV
  target/riscv: Make VSTIP and VSEIP read-only in hip
  target/riscv: Adjust privilege level for HLV(X)/HSV instructions
  target/riscv: flush TLB pages if PMP permission has been changed
  target/riscv: add log of PMP permission checking
  target/riscv: propagate PMP permission to TLB page
  hw/char: disable ibex uart receive if the buffer is full
  target/riscv: fix vs() to return proper error code

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