acpi: fix "Memory device control fields" register

acpi: fix "Memory device control fields" register

0 bit in Memory device control fields must be cleared before writing to
register. But now this field isn't cleared when other fields are written.

To solve this bug, This patch fixes UpdateRule to WriteAsZeros in "Memory
device control fields" register.

Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: Zhu Guihua <zhugh.fnst@cn.fujitsu.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>