Merge remote-tracking branch...

Merge remote-tracking branch 'remotes/mcayland/tags/qemu-openbios.for-upstream-20180831' into staging

qemu-openbios.for-upstream queue

# gpg: Signature made Fri 31 Aug 2018 12:26:55 BST
# gpg:                using RSA key 5BC2C56FAE0F321F
# gpg: Good signature from "Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>"
# Primary key fingerprint: CC62 1AB9 8E82 200D 915C  C9C4 5BC2 C56F AE0F 321F

* remotes/mcayland/tags/qemu-openbios.for-upstream-20180831:
  Update OpenBIOS images to a1280807 built from submodule.

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