[clang] [llvm] [SPIRV] Handle AMDGPU buffers in AMDGCN flavoured SPIR-V (PR #199376)

[Vyacheslav Levytskyy via cfe-commits]

VyacheslavLevytskyy wrote:

An obvious problem with the quick path of appropriation of DeviceOnlyINTEL/HostOnlyINTEL is that Storage Class stops having a semantic meaning by itself, and we are able to interpret it only in the context of a vendor. The standard extension mechanism guarantees that a SPIR-V module can be interpreted in the context of its OpExtension instructions, denoting extensions that added semantics referred by the module. Vendor info as a source of truth is a shift from "SPIR-V module can be interpreted with the specification and extension docs" premise.

https://github.com/llvm/llvm-project/pull/199376