ltd_idx is used as unsigned.

Signed-off-by: Dmitry Eremin <dmitry.eremin@intel.com>
Change-Id: Iae119e03b4cb58dddca2ce230d963d380255a57a
Reviewed-on: http://review.whamcloud.com/11879


Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>