Convert the kobj_map code to use a mutex instead of a semaphore.  It
converts the single two users as well, genhd.c and char_dev.c.

Signed-off-by: Jes Sorensen <jes@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>