ACPICA: Object repair: Allow 0-length packages for variable-length packages

For the predefined names that return fully variable-length
packages, allow a zero-length package with no warning, since it
is technically a legal construct (and BIOS writers use it.)
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/acpica/nsprepkg.c

@@ -112,9 +112,15 @@ acpi_ns_check_package(struct acpi_predefined_data *data,
 	elements = return_object->package.elements;
 	count = return_object->package.count;
 
-	/* The package must have at least one element, else invalid */
-
+	/*
+	 * Most packages must have at least one element. The only exception
+	 * is the variable-length package (ACPI_PTYPE1_VAR).
+	 */
 	if (!count) {
+		if (package->ret_info.type == ACPI_PTYPE1_VAR) {
+			return (AE_OK);
+		}
+
 		ACPI_WARN_PREDEFINED((AE_INFO, data->pathname, data->node_flags,
 				      "Return Package has no elements (empty)"));