[llvm] [SPIR-V] Fix LinkageAttribute emission for Vulkan (PR #143902)

[Steven Perron via llvm-commits]

s-perron wrote:

I don't think we want to do this. For HLSL, function explicitly marked with the `export` keyword will have to have the linkage attribute. The solution for this problem for HLSL is https://github.com/llvm/wg-hlsl/blob/main/proposals/0026-symbol-visibility.md

https://github.com/llvm/llvm-project/pull/143902