acpi: strip compiler info in built-in DSDT

acpi: strip compiler info in built-in DSDT

IASL stores it's revision in each table header it generates.
That's not nice since guests will see a change each time they move
between hypervisors.  We generally fill our own info for tables, but we
(and seabios) forgot to do this for the built-in DSDT.

Modifications in DSDT table:
 OEM ID:            "BXPC" -> "BOCHS "
 OEM Table ID:      "BXDSDT" -> "BXPCDSDT"
 Compiler ID:       "INTL" -> "BXPC"
 Compiler Version:  0x20130823 -> 0x00000001

Tested-by: Marcel Apfelbaum <marcel.a@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>