[AArch32] Add patterns for VCVT{A,N,P,M}.

Patterns for lowering libm calls to VCVT{A,N,P,M} are also included.
Phabricator Revision: http://reviews.llvm.org/D5033

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216388 91177308-0d34-0410-b5e6-96231b3b80d8