Add support for __nvvm_reflect changes in libdevice in CUDA-7.0

Summary:
CUDA 7.0's libdevice uses slightly different IR to call __nvvm_reflect
and that triggers an assertion in nvvm_reflect optimization pass. This
change allows nvvm_reflect pass to deal with both old and new ways to
pass an argument to __nvvm_reflect.

Test Plan: ninja check-all

Reviewers: eliben, echristo

Subscribers: jholewinski, llvm-commits

Differential Revision: http://reviews.llvm.org/D8399

llvm-svn: 232732