math: convert textflags from numbers to symbols

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/12773044
diff --git a/src/pkg/math/mod_arm.s b/src/pkg/math/mod_arm.s
index 47c564b..1f51588 100644
--- a/src/pkg/math/mod_arm.s
+++ b/src/pkg/math/mod_arm.s
@@ -2,5 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-TEXT ·Mod(SB),7,$0
+#include "../../cmd/ld/textflag.h"
+
+TEXT ·Mod(SB),NOSPLIT,$0
 	B ·mod(SB)