acpi: strip compiler info in built-in DSDT if any

IASL stores it's revision in each table header it generates.
That's a problem since guests see a change each time
they move between hypervisors.
We generally fill our own info for tables,
but we forgot to do this for the built-in DSDT.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>