vet: LEA* opcodes don't need to have matching length source and destination.
vet: LEA* opcodes don't need to have matching length source and destination.

LGTM=rsc
R=golang-codereviews, khr, rsc
CC=golang-codereviews
https://codereview.appspot.com/117950044

skyportsystems/go.tools,webfd/go-zh.tools,webfd/go-zh.tools,bryanxu/go-zh.tools,d0f/go-zh.tools,d0f/go-zh.tools,bryanxu/go-zh.tools,bryanxu/go-zh.tools,d0f/go-zh.tools,d0f/go-zh.tools,8limbs/gotools,webfd/go-zh.tools,8limbs/gotools,d0f/go-zh.tools,bryanxu/go-zh.tools,webfd/go-zh.tools,skyportsystems/go.tools,bryanxu/go-zh.tools,skyportsystems/go.tools,webfd/go-zh.tools,skyportsystems/go.tools,skyportsystems/go.tools,8limbs/gotools