[llvm] [Offload] Only initialize a plugin if it is needed (PR #92765)

[Joseph Huber via llvm-commits]

jhuber6 wrote:

@ronlieb AMD version https://github.com/llvm/llvm-project/issues/93183. It only required moving some code because AOMP has the logging stuff.

https://github.com/llvm/llvm-project/pull/92765