Revert "staging: Disable lustre file system for MIPS, SH, and XTENSA"

This reverts commit 16f1eeb6.

The reason for this patch was that lustre used copy_from_user_page.
Commit 76133e66

 ("staging/lustre: Replace jobid acquiring with per
node setting") removed that usage.
So the arch restrictions can go.

Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>