kthread: modify kernel-doc function name to match code

kthread: modify kernel-doc function name to match code

kthread.c:1073: warning: expecting prototype for kthread_create_worker(). Prototype was for kthread_create_worker_on_node() instead

Fixes: 41f70d8e1634 ("kthread: Unify kthread_create_on_cpu() and kthread_create_worker_on_cpu() automatic format")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Frederic Weisbecker <frederic@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>