sched_feat_write() should update ppos instead of file->f_pos.

(This reduces some BKL dependencies of this code.)
Signed-off-by: NJan Blunck <jblunck@suse.de>
Cc: jkacur@redhat.com
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jamie Lokier <jamie@shareable.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
LKML-Reference: <1258735245-25826-8-git-send-email-jblunck@suse.de>
Signed-off-by: NIngo Molnar <mingo@elte.hu>