Merge remote-tracking branch 'remotes/alistair/tags/pull-riscv-to-apply-20210624-2' into staging

Third RISC-V PR for 6.1 release

 - Fix MISA in the DisasContext
 - Fix GDB CSR XML generation
 - QOMify the SiFive UART
 - Add support for the OpenTitan timer

# gpg: Signature made Thu 24 Jun 2021 13:00:26 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-20210624-2:
  hw/riscv: OpenTitan: Connect the mtime and mtimecmp timer
  hw/timer: Initial commit of Ibex Timer
  hw/char/ibex_uart: Make the register layout private
  hw/char: QOMify sifive_uart
  hw/char: Consistent function names for sifive_uart
  target/riscv: gdbstub: Fix dynamic CSR XML generation
  target/riscv: Use target_ulong for the DisasContext misa

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