[NVPTX] Ignore target-cpu and -features for inlining

We don't want to prevent inlining because of target-cpu and -features
attributes that were added to newer versions of LLVM/Clang: There are
no incompatible functions in PTX, ptxas will throw errors in such cases.

Differential Revision: https://reviews.llvm.org/D47691

llvm-svn: 334904