[AArch64] Adjust the cost model for Exynos M1 and M2

Add new predicate to more accurately model the cost of arithmetic and
logical operations shifted left.

Differential revision: https://reviews.llvm.org/D37151

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@311943 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed