Currently there are cases where an XOR with -1 followed by an AND
is generanted when it could be done with just an ANDN instruction.

Changes to PPC64.rules and required files allows this change
in generated code.  Examples of this occur in sha3 among others.

Fixes: #18918

Change-Id: I647cb9b4a4aaeebb27db85f8bf75487d78f720c9
Reviewed-on: https://go-review.googlesource.com/36218
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Carlos Eduardo Seo <cseo@linux.vnet.ibm.com>