Fixes the following warning

 fetch.c: In function 'classify_eightbyte':
 fetch.c:377:33: error: 'cls2' may be used uninitialized in this function [-Werror=maybe-uninitialized]
    else if (cls == CLASS_INTEGER || cls2 == CLASS_INTEGER)
                                     ^

--- sysdeps/linux-gnu/x86/fetch.c
+++ sysdeps/linux-gnu/x86/fetch.c
@@ -461,6 +461,7 @@
 	switch (info->type) {
 		struct arg_type_info flattened;
 	case ARGTYPE_VOID:
+		classes[0] = CLASS_NO;
 		return 0;
 
 	case ARGTYPE_CHAR: