[llvm] [SPIRV] Add explicit layout (PR #135789)

[Vyacheslav Levytskyy via llvm-commits]

https://github.com/VyacheslavLevytskyy commented:

I think this should work for the compute part without problems, but I'd like to notify about the change @michalpaszkowski and @MrSidims, so that they are able to check this PR in advance with OpenCL CTS and SYCL CTS in case if they decide that it's worth double checking with extended test suites. The point is that compute environments are quite sensitive to correct types and we used to check big changes in types with CTS to be sure that all works. 

https://github.com/llvm/llvm-project/pull/135789