crypto/internal/fips140: use hash.Hash

crypto/internal/fips140: use hash.Hash

Since package hash is just the interface definition, not an
implementation, we can make a good argument that it doesn't impact the
security of the module and can be imported from outside.

For #69521

Change-Id: I6a6a4656b9c3cac8bb9ab8e8df11fa3238dc5d1d
Reviewed-on: https://go-review.googlesource.com/c/go/+/674917
Reviewed-by: Roland Shoemaker <roland@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Daniel McCarney <daniel@binaryparadox.net>
Reviewed-by: David Chase <drchase@google.com>
Auto-Submit: Filippo Valsorda <filippo@golang.org>