sched/doc: Fix generation of device-drivers

Since commit 7a6354e241d8 ("sched: Move wait.c into kernel/sched/"), the path
of this file has changed.

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Cc: jkosina@suse.cz
Cc: akpm@linux-foundation.org
Cc: linux-doc@vger.kernel.org
Cc: rob@landley.net
Cc: joe@perches.com
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1384937428-15731-1-git-send-email-nicolas.dichtel@6wind.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>