Merge remote-tracking branch 'remotes/alistair/tags/pull-riscv-to-apply-20210117-3' into staging

First RISC-V PR for 6.0

This PR:
 - Fixes some issues with the m25p80
 - Improves GDB support for RISC-V
 - Fixes some Linux boot issues, specifiaclly 32-bit boot failures
 - Enforces PMP exceptions correctly
 - Fixes some Coverity issues

# gpg: Signature made Sun 17 Jan 2021 21:53:19 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-20210117-3:
  riscv: Pass RISCVHartArrayState by pointer
  target/riscv: Remove built-in GDB XML files for CSRs
  target/riscv: Generate the GDB XML file for CSR registers dynamically
  target/riscv: Add CSR name in the CSR function table
  target/riscv: Make csr_ops[CSR_TABLE_SIZE] external
  hw/misc/sifive_u_otp: handling the fails of blk_pread and blk_pwrite
  hw/riscv: sifive_u: Use SIFIVE_U_CPU for mc->default_cpu_type
  target/riscv/pmp: Raise exception if no PMP entry is configured
  RISC-V: Place DTB at 3GB boundary instead of 4GB
  gdb: riscv: Add target description
  hw/block: m25p80: Implement AAI-WP command support for SST flashes
  hw/block: m25p80: Don't write to flash if write is disabled

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