acpi-build: simplify rsdp management for legacy

acpi-build: simplify rsdp management for legacy

For legacy machine types, rsdp is not in RAM, so we need a copy of rsdp
for fw cfg. We previously used g_array_free with false parameter,
but this seems to confuse people.
This also wastes a bit of memory as the buffer is unused for new
machine types.

Let's just use plain g_memdup, and free original memory together with
the array.

TODO: rationalize tcpalog memory management, and get rid of the mfre
parameter.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>