Add log callback for opencl

[thewh1teagle]

I think currently there is no such way to trampoline opencl log. whisper.cpp doesn't allow setting a log callback in ggml-opencl.cpp

https://github.com/ggerganov/whisper.cpp/blob/af5833e29819810f2d83228228a9a3077e5ccd93/ggml-opencl.cpp#L1103-L205

as a comparison, the ggml_metal backend allows this

https://github.com/ggerganov/whisper.cpp/blob/af5833e29819810f2d83228228a9a3077e5ccd93/ggml-metal.h#L43C15-L43C50

As a result, I always see output such as

ggml_opencl: selecting platform: 'AMD Accelerated Parallel Processing'
ggml_opencl: selecting device: 'gfx902'

Can you add a way to to register log callback in ggml opencl?

Thanks

Related: https://github.com/tazz4843/whisper-rs/issues/155