internal/bytealg: remove aix and linux build tags from ppc64 index code
This code is generic to ppc64/ppc64le - there is no need to limit it to
aix or linux.
Updates #56001
Change-Id: I613964a90f9c5ca637720219a0260d65427f4be0
Reviewed-on: https://go-review.googlesource.com/c/go/+/473697
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Joel Sing <joel@sing.id.au> Reviewed-by: Carlos Amedee <carlos@golang.org> Reviewed-by: Lynn Boger <laboger@linux.vnet.ibm.com>