cmd/6c: fix probable code gen bug
cmd/6c: fix probable code gen bug

This is a pointer being copied; MOVL can't possibly be right.

R=ken2
CC=golang-dev
http://codereview.appspot.com/5999043
abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go