Merge remote-tracking branch 'remotes/mcayland/tags/qemu-openbios-20200521' into staging

qemu-openbios queue

# gpg: Signature made Thu 21 May 2020 21:02:44 BST
# gpg:                using RSA key CC621AB98E82200D915CC9C45BC2C56FAE0F321F
# gpg:                issuer "mark.cave-ayland@ilande.co.uk"
# gpg: Good signature from "Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>" [full]
# Primary key fingerprint: CC62 1AB9 8E82 200D 915C  C9C4 5BC2 C56F AE0F 321F

* remotes/mcayland/tags/qemu-openbios-20200521:
  Update OpenBIOS images to 4704d9eb built from submodule.

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