gallium/radeon: clean up HAVE_LLVM #ifdefs in r600_get_llvm_processor_name
gallium/radeon: clean up HAVE_LLVM #ifdefs in r600_get_llvm_processor_name

Reviewed-by: Nicolai Hähnle <0d0be6cf5ad662651be2dc5dfd44aa2b09d4c1cc@amd.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler