[coroutines] Add missing pass dependency.

Summary:
CoroSplit depends on CallGraphWrapperPass, but it was not explicitly adding it as a pass dependency.

This missing dependency can trigger errors / assertions / crashes in PMTopLevelManager::schedulePass() under certain configurations.

Author: ben-clayton

Reviewers: GorNishanov

Reviewed By: GorNishanov

Subscribers: capn, EricWF, modocache, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D63144

llvm-svn: 363727