[flang] Fix type resolution in ConcurrentHeader

As it was implemented we weren't detecting non-constant kind parameters
in the integer-type-spec. The fix is just to walk the integer-type-spec
like was do any other one.

Also, there is not need for ResolveControlExpressions -- all it does is
walk that part of the parse tree.

Original-commit: flang-compiler/f18@8c0d890eb8852e460ea247c0c0e873dfe2da0200
Reviewed-on: https://github.com/flang-compiler/f18/pull/904
Tree-same-pre-rewrite: false