[llvm] [NVPTX] Auto-Upgrade some nvvm.annotations to attributes (PR #119261)

[Adrian Kuegel via llvm-commits]

akuegel wrote:

Ok, I found a fix with the help of @d0k, it seems now we need to also set the calling convention of the function to llvm::CallingConv::PTX_Kernel, as the legacy annotations are not accepted anymore (the change to `isKernelFunction` in `NVPTXUtilities.h`)

https://github.com/llvm/llvm-project/pull/119261