Use pagecache_write to avoid shmemfs clearing the pages prior to us
immediately overwriting them with our data.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/20170317194648.12468-2-chris@chris-wilson.co.ukReviewed-by: NMatthew Auld <matthew.auld@intel.com>