Fourth RISC-V PR for 6.1 release

 - Code cleanups
 - Documentation improvements
 - Hypervisor extension improvements with hideleg and hedeleg
 - sifive_u fixes
 - OpenTitan register layout updates
 - Fix coverity issue

# gpg: Signature made Thu 15 Jul 2021 08:14:00 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-20210715:
  hw/riscv/boot: Check the error of fdt_pack()
  hw/riscv: opentitan: Add the flash alias
  hw/riscv: opentitan: Add the unimplement rv_core_ibex_peri
  char: ibex_uart: Update the register layout
  hw/riscv: sifive_u: Make sure firmware info is 8-byte aligned
  hw/riscv: sifive_u: Correct the CLINT timebase frequency
  docs/system: riscv: Update Microchip Icicle Kit for direct kernel boot
  target/riscv: hardwire bits in hideleg and hedeleg
  docs/system: riscv: Add documentation for virt machine
  docs/system: riscv: Fix CLINT name in the sifive_u doc
  target/riscv: csr: Remove redundant check in fp csr read/write routines
  target/riscv: pmp: Fix some typos

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