[llvm] [XCOFF] Support the subtype in Dwarf section headers (PR #81667)

[via llvm-commits]

stephenpeckham wrote:

I meant to remove the llvm-readobj call from dwarf-subsection-types.yaml. That portion of the test is removed now.  For llvm-readobj/XCOFF/sections.test, I had followed the existing test and left all the file header fields in the FileCheck patterns.  But now I've changed the test for the dwarf section headers to only check the relevant fields.

https://github.com/llvm/llvm-project/pull/81667