staging/lustre/llite: move /proc/fs/lustre/llite/xattr_cache to sysfs

Move xattr_cache file from /proc/fs/lustre/llite/*
to /sys/fs/lustre/llite/*/

Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>