Upstream OpenBIOS now implements SBus probing in order to determine the
contents of a physical bus slot, which is required to allow OpenBIOS to
identify the framebuffer without help from the fw_cfg interface.

SBus probing works by detecting the presence of an FCode program
(effectively tokenised Forth) at the base address of each slot, and if
present executes it so that it creates its own device node in the
OpenBIOS device tree.

The FCode ROM is generated as part of the OpenBIOS build and should
generally be updated at the same time.
Signed-off-by: NMark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
CC: Blue Swirl <blauwirbel@gmail.com>
CC: Bob Breuer <breuerr@mc.net>
CC: Artyom Tarasenko <atar4qemu@gmail.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>