acpi: Add missing GCC_FMT_ATTR

This fixes a compiler warning when compiling with -Wextra.

Signed-off-by: Stefan Weil <sw@weilnetz.de>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

include/hw/acpi/aml-build.h

@@ -369,6 +369,7 @@ build_rsdt(GArray *table_data, GArray *linker, GArray *table_offsets,
            const char *oem_id, const char *oem_table_id);
 
 int
-build_append_named_dword(GArray *array, const char *name_format, ...);
+build_append_named_dword(GArray *array, const char *name_format, ...)
+GCC_FMT_ATTR(2, 3);
 
 #endif