Revert "Disable -mcpu=cortex-a15 flag for krait"

This reverts commit d3694caec8b51697c5afd76a3da0f550352ae3dd.

Change-Id: I834ea48d117c99860862dc0c7fff217b8c22c184
Merge "Revert "Disable -mcpu=cortex-a15 flag for krait"" into lp5.0