runtime: cull dead code

They are unused, and vet wants them to have
a function prototype.

Updates #11041

Change-Id: Idedc96ddd3c3cf1b1d2ab6d98796367eab29f032
Reviewed-on: https://go-review.googlesource.com/27492
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/runtime/asm.s

@@ -12,8 +12,5 @@ DATA runtime·no_pointers_stackmap+0x00(SB)/4, $2
 DATA runtime·no_pointers_stackmap+0x04(SB)/4, $0
 GLOBL runtime·no_pointers_stackmap(SB),RODATA, $8
 
-TEXT runtime·nop(SB),NOSPLIT,$0-0
-	RET
-
 GLOBL runtime·mheap_(SB), NOPTR, $0
 GLOBL runtime·memstats(SB), NOPTR, $0

src/runtime/internal/atomic/asm.s

-// Copyright 2015 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-#include "textflag.h"
-
-TEXT runtime∕internal∕atomic·nop(SB),NOSPLIT,$0-0
-	RET

src/runtime/internal/atomic/sys_nacl_arm.s

@@ -4,9 +4,6 @@
 
 #include "textflag.h"
 
-TEXT runtime∕internal∕atomic·Casp(SB),NOSPLIT,$0
-	B	runtime·cas(SB)
-
 // This is only valid for ARMv6+, however, NaCl/ARM is only defined
 // for ARMv7A anyway.
 TEXT runtime∕internal∕atomic·Cas(SB),NOSPLIT,$0