pc: acpi: force FADT rev1 for 440fx based machine types

w2k used to boot on QEMU until revision of FADT has
been bumped to rev3
(commit 77af8a2b hw/i386: Use Rev3 FADT (ACPI 2.0) instead of Rev1 to improve guest OS support.)

Keep PC machine at rev1 to remain compatible and Q35
at rev3 where w2k isn't supported anyway so OSX could
run as well.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Tested-by: John Arbuckle <programmingkidx@gmail.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>