tests: acpi: reuse fetch_table() in vmgenid-test

tests: acpi: reuse fetch_table() in vmgenid-test

Move fetch_table() into acpi-utils.c renaming it to acpi_fetch_table()
and reuse it in vmgenid-test that reads RSDT and then tables it references,
to find and parse VMGNEID SSDT.
While at it wrap RSDT referenced tables enumeration into FOREACH macro
(similar to what we do with QLIST_FOREACH & co) to reuse it with bios and
vmgenid tests.

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