LU-8560 libcfs: handle PAGE_CACHE_* removal in newer kernels

LU-8560 libcfs: handle PAGE_CACHE_* removal in newer kernels

Starting with linux kernel 4.6 all the PAGE_CACHE_* defines
have been removed. Now it is required to use PAGE_* instead.
This is a simple blanket change since PAGE_CACHE_* was always
the same as PAGE_*.

Change-Id: I3ba8954d44969e2473afa939bbb8b8b5b1345446
Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-on: http://review.whamcloud.com/22206
Tested-by: Maloo <hpdd-maloo@intel.com>
Tested-by: Jenkins
Reviewed-by: Frank Zago <fzago@cray.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>