This adds some AArch64 specific smul_with_overflow and umul_with_overflow
costs, overriding the default costs. The code generation for these mul
with overflow intrinsics is usually better than the default expansion on
AArch64. The costs come from https://godbolt.org/z/zEzYhMWqo with various
types, or llvm/test/CodeGen/AArch64/arm64-xaluo.ll.
Differential Revision: https://reviews.llvm.org/D116732
c65270cf96