kobject: Make Documentation/kobject.txt a little more coherent.

While reading Documentation/kobject.txt:

  Note kobject_rename does perform any locking or have a solid notion of
  what names are valid so the provide must provide their own sanity checking
  and serialization.

I expect better: You never see me hard with time word making sentence
coherent stuff.  Ever.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>