Make it possible to boot a versatile machine in qemu.

Boot command:
 /usr/bin/qemu-system-arm -cpu arm926 -machine versatilepb \
  -nographic -nic none -m 256M -monitor none -no-reboot \
  -kernel zImage -dtb versatile-pb.dtb \
  -append "console=ttyAMA0,115200 rootwait root=/dev/vda" \
  -drive armv5_rootfs.ext4,if=none,format=raw,id=hd0 \
  -device virtio-blk-pci,drive=hd0

When doing build and boot testing, it makes more sense to enable arch
vesatile, serial amba_pl011 and virtio (mmio|blk|pci) to
multi_v5_defconfig to make that boot out of the box, with a modern
virtio (mmio|blk|pci) driver. Using the above commandline. Another way
to build and boot would be to use tuxmake/tuxrun. Tuxmake [1] builds the
kernel, and Tuxrun [2] boots the kernel in qemu. Both projects uses
podman to do the build/tests inside.  This makes both project a good
tool to use when finding a regression that you would like someone else
to reproduce with the exact same setup.

tuxmake --runtime podman --target-arch arm \
        --toolchain gcc-11 --kconfig multi_v5_defconfig
tuxrun --tuxmake ~/.cache/tuxmake/builds/3072 --device qemu-armv5

[1] https://tuxmake.org/
[2] https://tuxrun.org/Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
Link: https://lore.kernel.org/r/20220308121933.3967868-1-anders.roxell@linaro.org'
Signed-off-by: Arnd Bergmann <arnd@arndb.de>