defconfig feature: add FORCE_SILICON_PERFORMANCE for higher CPU Ghz settings

Change-Id: I0faf235528637d080d1044ca1c7351e7be1d11d2
clean up FORCE_SILICON handling

Change-Id: I5cc786a8ff5a4364f4458a9919b9863bae57fd55
Merge remote-tracking branch 'kfire/cm-10.1' into cm-10.1-exp