[JFFS2] Quiet lockdep false positive.

Don't hold f->sem while calling into jffs2_do_create(). It makes lockdep
unhappy, and we don't really need it -- the _reason_ it's a false
positive is because nobody else can see this inode yet and so nobody
will be trying to lock it anyway.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>