runtime: fix comment for hwcap on linux/arm

hwcap is set in archauxv, setup_auxv no longer exists.

Change-Id: I0fc9393e0c1c45192e0eff4715e9bdd69fab2653
Reviewed-on: https://go-review.googlesource.com/99779Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/runtime/os_linux_arm.go

@@ -16,7 +16,7 @@ const (
 
 var randomNumber uint32
 var armArch uint8 = 6 // we default to ARMv6
-var hwcap uint32      // set by setup_auxv
+var hwcap uint32      // set by archauxv
 var hardDiv bool      // set if a hardware divider is available
 
 func checkgoarm() {