test: enable fixedbugs/issue10607.go test on linux/mips64x

external linking is now supported.

Change-Id: I13e90c39dad86e60781adecdbe8e6bc9e522f740
Reviewed-on: https://go-review.googlesource.com/19811Reviewed-by: Minux Ma <minux@golang.org>

test/fixedbugs/issue10607.go

-// +build linux,!ppc64,!ppc64le,!mips64,!mips64le
+// +build linux,!ppc64,!ppc64le
 // run
 
 // Copyright 2015 The Go Authors. All rights reserved.