[ARM] Relax restriction on variadic functions for tailcall optimization

Summary:
Variadic functions can be treated in the same way as normal functions
with respect to the number and types of parameters.

Reviewers: grosbach, olista01, t.p.northover, rengolin

Subscribers: javed.absar, aemerson, llvm-commits

Differential Revision: https://reviews.llvm.org/D26748

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@287219 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed