acpi_extract.py: document DEVICE directives

commit 2b568ebb20b08c7881d976b5bc9f59a425bae5e6
    acpi_extract: detect DeviceOp
added new directives to acpi_extract.py, but didn't
document them.
Add documentation at top of file.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
1 file changed