crypto/internal/fips/aes: add CAST

crypto/internal/fips/aes: add CAST

For #69536

Change-Id: I6ecbe8b05f9f01afe2aa32c59fc56c9e1c6ea6b4
Reviewed-on: https://go-review.googlesource.com/c/go/+/626437
Reviewed-by: Daniel McCarney <daniel@binaryparadox.net>
Reviewed-by: Roland Shoemaker <roland@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Auto-Submit: Filippo Valsorda <filippo@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>