workqueue: Don't call va_start / va_end twice

Calling va_start / va_end multiple times is undefined and causes
problems with certain compiler / platforms.

Change alloc_ordered_workqueue_lockdep_map to a macro and updated
__alloc_workqueue to take a va_list argument.

Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Tejun Heo <tj@kernel.org>