[AArch64] Add pipeline model for Exynos M3

Add the scheduling and cost model for Exynos M3.

Differential revision: https://reviews.llvm.org/D42387

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@323773 91177308-0d34-0410-b5e6-96231b3b80d8
10 files changed