LU-6142 lustre: introduce CONFIG_LUSTRE_FS_POSIX_ACL

LU-6142 lustre: introduce CONFIG_LUSTRE_FS_POSIX_ACL

Lustre (or any file system) should not conditionally
compile code based on CONFIG_FS_POSIX_ACL.  This config
option enables library support.
A file system can define it's own config option,
which then selects CONFIG_FS_POSIX_ACL (if needed).  It should
act on its own option, not the library one.

This patch makes that change.

While lustre is out-of-tree, it cannot select CONFIG_FS_POSIX_ACL
and must work with the configruation of the kernel it is being built
against. So the new CONFIG_LUSTRE_FS_POSIX_ACL can only be selected
if the based kernel has CONFIG_FS_POSIX_ACL selected. With that
restriction this change becomes little more than an indirection.
However it means that the out-of-tree code can be closer to the
(eventual) in-tree code.

Test-Parameters: trivial

Signed-off-by: NeilBrown <neilb@suse.com>
Change-Id: I3ba283f295d1c7217e7ff9917573be0fe92bb2ca
Reviewed-on: https://review.whamcloud.com/36085
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Neil Brown <neilb@suse.de>
Reviewed-by: Petros Koutoupis <pkoutoupis@cray.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.super@gmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>