[GlobalsAA] Restrict ModRef result if any internal method has its address taken.

Summary:
If there are any internal methods whose address was taken, conclude there is nothing known in relation of any other internal method and a global.

Reviewers: nlopes, sanjoy.google

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D69690