Cycles OpenCL: Remove single program

Part of the cleanup of the OpenCL codebase.
Single program is not effective when using OpenCL, it is slower
to compile and slower during rendering (when used in for example
`barbershop` or `victor`).

Reviewers: brecht, #cycles

Maniphest Tasks: T62267

Differential Revision: https://developer.blender.org/D4481

intern/cycles/blender/blender_python.cpp

@@ -104,7 +104,6 @@ bool debug_flags_sync_from_scene(BL::Scene b_scene)
 	/* Synchronize other OpenCL flags. */
 	flags.opencl.debug = get_boolean(cscene, "debug_use_opencl_debug");
 	flags.opencl.mem_limit = ((size_t)get_int(cscene, "debug_opencl_mem_limit"))*1024*1024;
-	flags.opencl.single_program = get_boolean(cscene, "debug_opencl_kernel_single_program");
 	return flags.opencl.device_type != opencl_device_type;
 }