[CUDA] Emit errors for wrong-side calls made on the same line as non-wrong-side calls.

Summary:
This fixes two related bugs:

1) Previously, if you had a non-wrong side call at some source code
location L, we wouldn't emit errors for wrong-side calls that appeared
at L.

2) We'd only emit one wrong-side error per source code location, when we
actually want to emit it twice if we hit this line more than once due to
e.g. template instantiation.

Reviewers: tra

Subscribers: rnk, cfe-commits

Differential Revision: https://reviews.llvm.org/D25702

llvm-svn: 284643