Revert "modified makefile to not conflict with krait opt"

This reverts commit 9c8a39ba9c9d18d2819c665889a24fa19a5addf4.
Revert "ARM: Use -mcpu=cortex-a15 when targeting MSM Krait CPUs"

This reverts commit aeed95f935d12c7253ed96f7523b0f71a43f0aff.