ChromeOS: Refactor ACPI CNVS generation

Remove chromeos_dsdt_generator() calls under mainboard, it
is possible to make the single call to fill \CNVS and
\OIPG without leveraging device operations.

Change-Id: Id79af96bb6c038d273ac9c4afc723437fc1f3fc9
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/55502
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>

src/vendorcode/google/chromeos/gnvs.c

@@ -98,7 +98,14 @@ void acpi_fill_cnvs(void)
 {
 	const struct opregion cnvs_op = OPREGION("CNVS", SYSTEMMEMORY, (uintptr_t)chromeos_acpi,
 						 sizeof(*chromeos_acpi));
+
+	if (!chromeos_acpi)
+		return;
+
 	acpigen_write_scope("\\");
 	acpigen_write_opregion(&cnvs_op);
 	acpigen_pop_len();
+
+	/* Usually this creates OIPG package for GPIOs. */
+	mainboard_chromeos_acpi_generate();
 }