Correcting values is allowed per the syscall package rules, so update
these constants to their correct value on ppc64/ppc64le. The values now
match the corresponding constants in x/sys/unix.

Update #19560
Fixes #22000

Change-Id: I1d358de345766ec96e15dfcc8911fe2f39fb0ddb
Reviewed-on: https://go-review.googlesource.com/66510
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Lynn Boger <laboger@linux.vnet.ibm.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>