On RISC-V QEMU provides an XSDT table. The RSDP table points to it.
We must not zero out this pointer because otherwise no ACPI table can be
found.
Fixes: 15ca25e31e ("x86: emulation: Support BLOBLIST_TABLES properly")
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>