This patch enables PostRAScheduler specifically for AArch64 generic build,
which is beneficial from the performance perspective.
Speedups up to 2 to 7% for some benchmarks on A57 and A53 are observed.
Also benchmarks from LLVM test-suite did not regress.
Differential Revision: http://reviews.llvm.org/D15557
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@255896
91177308-0d34-0410-b5e6-
96231b3b80d8