[llvm] [AMDGPU] Merge the conditions used for deciding CS spills for amdgpu_cs_chain[_preserve] (PR #109911)

[Christudasan Devadasan via llvm-commits]

cdevadas wrote:

This patch is required for landing my PR https://github.com/llvm/llvm-project/pull/93526.
I found some regressions while rebasing my PR into the latest upstream.

https://github.com/llvm/llvm-project/pull/109911