Fix a few tests that were missing ':' on CHECK lines and weren't testing anything.

Found by `git grep '\/\/ CHECK-[^: ]* ' clang/test/ | grep -v RUN:`.

Also tweak CodeGenCXX/arm-swiftcall.cpp to still pass now that it checks more.

Differential Revision: https://reviews.llvm.org/D58061

llvm-svn: 353744