This commit adds AIX operating system to time package for ppc64
architecture.

Updates: #25893

Change-Id: I4fb6fb47eae7671bf4e22729d6d160f557083c44
Reviewed-on: https://go-review.googlesource.com/c/138721
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>