staging: lustre: lprocfs: implement log2 using bitops

This patch implements log2 using fls.

Signed-off-by: Andrew Perepechko <andrew_perepechko@xyratex.com>
Reviewed-by: Alexander Boyko <Alexander_Boyko@xyratex.com>
Reviewed-by:  <alexander_zarochentsev@xyratex.com>
Reviewed-by: Vitaly Fertman <Vitaly_Fertman@xyratex.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-3496
Xyratex-bug-id: MRP-999
Reviewed-on: http://review.whamcloud.com/6757


Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>