[llvm] [AMDGPU] Replace relaxed-buffer-oob-mode feature with module flag (PR #160922)

[Matt Arsenault via llvm-commits]

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arsenm wrote:

Basically, this is an alias of strict that is allowed to link to non-strict modules. If you link to a strict module in the future, it needs to provide the strict behavior 

https://github.com/llvm/llvm-project/pull/160922