Refine the cl thread implement for queue.

Refine the cl thread implement for queue.

Because the cl_command_queue can be used in several threads simultaneously but
without add ref to it, we now handle it like this:
Keep one threads_slot_array, every time the thread get gpgpu or batch buffer, if it
does not have a slot, assign it.
The resources are keeped in queue private, and resize it if needed.
When the thread exit, the slot will be set invalid.
When queue released, all the resources will be released. If user still enqueue, flush
or finish the queue after it has been released, the behavior is undefined.
TODO: Need to shrink the slot map.

Signed-off-by: Junyan He <junyan.he@linux.intel.com>
Reviewed-by: Zhigang Gong <zhigang.gong@linux.intel.com>