[modules] This check is run before we resolve the header, not after, so just

[modules] This check is run before we resolve the header, not after, so just
check that private headers are in a list matching the role. (We can't perform
the opposite checks for non-private headers because we infer those.)

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@231728 91177308-0d34-0410-b5e6-96231b3b80d8