go.tools/go/types: cleanup: remove unnecessary receiver
go.tools/go/types: cleanup: remove unnecessary receiver

R=adonovan
CC=golang-codereviews
https://codereview.appspot.com/53810044

lattera/go.tools,chenjianlong/go.tools,karmakaze/go.tools,chenjianlong/go.tools,karmakaze/go.tools,karmakaze/go.tools,chenjianlong/go.tools,lattera/go.tools,karmakaze/go.tools,karmakaze/go.tools,lattera/go.tools