misc/cgo/gmp: fix typo.
misc/cgo/gmp: fix typo.

R=golang-dev, minux
CC=golang-dev
https://codereview.appspot.com/8174045

Committer: Shenghou Ma <b563c57947dc20eb81988e3e3c22786764c14ca8@gmail.com>
abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go