Merge remote-tracking branch 'remotes/alistair/tags/pull-riscv-to-apply-20201113...

Merge remote-tracking branch 'remotes/alistair/tags/pull-riscv-to-apply-20201113-1' into staging

Two small additional fixes for the Ibex PLIC.

# gpg: Signature made Sat 14 Nov 2020 05:44:22 GMT
# gpg:                using RSA key F6C4AC46D4934868D3B8CE8F21E10D29DF977054
# gpg: Good signature from "Alistair Francis <[email protected]>" [full]
# Primary key fingerprint: F6C4 AC46 D493 4868 D3B8  CE8F 21E1 0D29 DF97 7054

* remotes/alistair/tags/pull-riscv-to-apply-20201113-1:
  intc/ibex_plic: Ensure we don't loose interrupts
  intc/ibex_plic: Fix some typos in the comments

Signed-off-by: Peter Maydell <[email protected]>