Do not define AFS_SYSCALL for ppc64le_linux26

Do not define AFS_SYSCALL for ppc64le_linux26

AFS_SYSCALL is defined to the syscall number we can use for a certain
platform (for pioctls and other AFS-specific kernel calls). On many
modern platforms, such as Linux, we don't use direct syscalls anymore,
instead routing our AFS-specific syscalls through an ioctl, and
AFS_SYSCALL is just used as a fallback for compatibility for older
OpenAFS releases that might still be using the syscall.

For new platforms, we have no need for this compatibility code path,
since there is no existing code we might need to be compatible with.
We should avoid defining AFS_SYSCALL for those, so we can avoid
manually-issuing syscalls in more cases. The ppc64le_linux26 platform
is a very new platform (introduced in 191e18eb "Open ppc64le_linux
sysname space"), and so should not have AFS_SYSCALL defined.

So, remove AFS_SYSCALL from ppc64le_linux26's param.h.

Reviewed-on: https://gerrit.openafs.org/13592
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Mark Vitale <mvitale@sinenomine.net>
Tested-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
(cherry picked from commit 46563f929a851032d785634763963808d6e2bfeb)

Change-Id: Ib161b50a9156d3790134de4e1a8e66a1356e0fb6
Reviewed-on: https://gerrit.openafs.org/13636
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>