x64 simd: Incorrect codegen leads to wrong result

Found with some fuzzing, this module:

```wasm
(module
  (func (result i64)
      v128.const i64x2 -1 1
      global.get 0
      f64x2.replace_lane 0
      i64x2.extract_lane 1
  )

  (global f64 (f64.const 1))
  (export "" (func 0)))
```

leads to:

```
$ wasmtime run --enable-simd --invoke '' test.wat
0
```

but the result should be 1

cc @jlb6740, @abrown 