ARM: remove floating-point patterns for @llvm.arm.neon.vabs

The front-end is now generating the generic @llvm.fabs for this
operation now, so the extra patterns are no longer needed.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201314 91177308-0d34-0410-b5e6-96231b3b80d8