LU-5275 obdclass: remove lproc_var argument to lprocfs_add_simple

LU-5275 obdclass: remove lproc_var argument to lprocfs_add_simple

The struct lproc_var argument is no longer used so we can
simplify the lprocfs_add_simple function.

Signed-off-by: James Simmons <uja.ornl@gmail.com>
Change-Id: I2099e92c9e93c67843a41fb8e46a481a75fbd004
Reviewed-on: http://review.whamcloud.com/11732
Tested-by: Jenkins
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>