Vectorize bitmap operations on A15 too

 * Commit a2e20761b5ad646ce3f08ed24995799dd81acee0 enables GCC
   vectorization for bitmap operations on Krait. Enable it on A15 also.

Change-Id: I1f733f5311376deb78782931ea2b83a8d12c2171
Revert "Vectorize bitmap operations on A15 too"

This reverts commit fcdafc52fe1ce9082823bc26ba99d604526669f5.