[CUDA] Simplify SemaCUDA/function-overload.cu test.

Summary:
Principally, don't hardcode the line numbers of various notes.  This
lets us make changes to the test without recomputing linenos everywhere.

Instead, just tell -verify that we may get 0 or more notes pointing to
the relevant function definitions.  Checking that we get exactly the
right note isn't so important (and anyway is checked elsewhere).

Reviewers: tra

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D18385

llvm-svn: 264206