util/mainboard/google/volteer: Add dptf.asl to the template

The dptf.asl is needed when creating a new volteer variant, otherwise,
it will make the variant build failed. The error could be found from
this link: https://review.coreboot.org/c/coreboot/+/42709

BUG=b:158797761
TEST=Generate the Delbin correctly

Signed-off-by: Zhuohao Lee <zhuohao@chromium.org>
Change-Id: Ib4059df9e08d6a1dba88f0299bb39c8c6ae406ae
Reviewed-on: https://review.coreboot.org/c/coreboot/+/42715
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Fagerburg <pfagerburg@chromium.org>

util/mainboard/google/volteer/template/include/variant/acpi/dptf.asl

@@ -0,0 +1,3 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include <baseboard/acpi/dptf.asl>