kobject: Replace ALL occurrences of '/' with '!' instead of only the first one.

A recent patch from Kay Sievers <kay.sievers@vrfy.org>
replaced the first occurrence of '/' with '!' as needed for block devices.

Now do some cheap defensive coding and replace all of them to avoid future
issues in this area.

Signed-off-by: Ingo Oeser <ioe-lkml@rameria.de>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>