[dev.simd] cmd/compile, simd: change DotProductQuadruple and add peepholes

[dev.simd] cmd/compile, simd: change DotProductQuadruple and add peepholes

This CL addressed some API change decisions in the API audit.
Instead of exposing the Intel format, we hide the add part of the
instructions under the peephole, and rename the API as
DotProdQuadruple

Change-Id: I471c0a755174bc15dd83bdc0f757d6356b92d835
Reviewed-on: https://go-review.googlesource.com/c/go/+/721420
Reviewed-by: David Chase <drchase@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>