[llvm] [AsmPrinter] Find a DIE's unit by its owner, not by its tag (PR #219660)

[Arcadiy Ivanov via llvm-commits]

arcivanov wrote:

Rewrote commit message and the PR description based on the feedback + a correction to the "We don't actually have to check the tag type, and instead we can just walk up the chain until there's no parent." The quote is inaccurate - we walk up and stopped based on DIEUnit owner, not the absence of a parent. 

https://github.com/llvm/llvm-project/pull/219660