hw/arm/aspeed: Add GB200 BMC target

hw/arm/aspeed: Add GB200 BMC target

GB200nvl72 is a system for for accelerated compute.  This is a model for
the BMC target within the system.

This is based on the device tree aspeed-bmc-nvidia-gb200nvl-bmc.dts
from:

[1] https://github.com/openbmc/linux/blob/dev-6.6/arch/arm/boot/dts/aspeed/aspeed-bmc-nvidia-gb200nvl-bmc.dts

Signed-off-by: Ed Tanous <etanous@nvidia.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/qemu-devel/20250703144249.3348879-4-etanous@nvidia.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>