libm: These optimizations are only for Krait

This fixes PowerAmp start issues

 * Issues on other chipsets. Resync with CAF and only use on specific
   chipsets (Krait, Sparrow).

Change-Id: I063aab23e9326bcb61f7a4fda0a00ab12ed3d53e
Signed-off-by: Dan Trifan <jimsth@gmail.com>