[ARM][NEON] Add support for ISD::ABS lowering 

Update NEON int_arm_neon_vabs intrinsic to use the ISD::ABS opcode directly

Added constant folding tests.

Differential Revision: https://reviews.llvm.org/D32938

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@302417 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed