The machine uses a modified U-Boot under GPL license but the sources
of it are lost with only a binary available so it cannot be included
in QEMU. Allow running without the firmware image which can be used
when calling a boot loader directly and thus simplifying booting
guests. We need a small routine that AmigaOS calls from ROM which is
added in this case to allow booting AmigaOS without external firmware
image.
Fixes: d9656f860a38 ("hw/ppc: Add emulation of AmigaOne XE board")
Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>