tracing/workqueue: Use %pf in workqueue trace events

Using %pf instead of %pF supresses printing of the function offset
which will always be 0 in the case of worklet functions.

Signed-off-by: Anton Blanchard <anton@samba.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Zhaolei <zhaolei@cn.fujitsu.com>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <20090922024033.GB31801@kryten>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>