acpi: build_facs: use build_append_int_noprefix() API to compose table

Drop usage of packed structures and explicit endian
conversions when building table and use endian agnostic
build_append_int_noprefix() API to build it.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Message-Id: <20210924122802.1455362-34-imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
index d9e2b5d..81418b7 100644
--- a/hw/i386/acpi-build.c
+++ b/hw/i386/acpi-build.c
@@ -345,13 +345,23 @@
     g_array_set_size(blob, ROUND_UP(acpi_data_len(blob), align));
 }
 
-/* FACS */
+/*
+ * ACPI spec 1.0b,
+ * 5.2.6 Firmware ACPI Control Structure
+ */
 static void
 build_facs(GArray *table_data)
 {
-    AcpiFacsDescriptorRev1 *facs = acpi_data_push(table_data, sizeof *facs);
-    memcpy(&facs->signature, "FACS", 4);
-    facs->length = cpu_to_le32(sizeof(*facs));
+    const char *sig = "FACS";
+    const uint8_t reserved[40] = {};
+
+    g_array_append_vals(table_data, sig, 4); /* Signature */
+    build_append_int_noprefix(table_data, 64, 4); /* Length */
+    build_append_int_noprefix(table_data, 0, 4); /* Hardware Signature */
+    build_append_int_noprefix(table_data, 0, 4); /* Firmware Waking Vector */
+    build_append_int_noprefix(table_data, 0, 4); /* Global Lock */
+    build_append_int_noprefix(table_data, 0, 4); /* Flags */
+    g_array_append_vals(table_data, reserved, 40); /* Reserved */
 }
 
 static void build_append_pcihp_notify_entry(Aml *method, int slot)