We have a function to calculate this, so update the code to use the function.

Change-ID: Ia345b6fe6ec7f0b2dcf1199471b0d0f959ad3908
Signed-off-by: Anjali Singhai Jain <anjali.singhai@intel.com>
Tested-by: Kavindya Deegala <kavindya.s.deegala@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>