i2o_scsi: handle sysfs failure

i2o_device:
 * convert i2o_device_add() to return integer error code
   rather than pointer.  Fortunately -nobody- checks the return code of
   this function, so changing has nil impact.
 * handle errors thrown by device_register()

More work in i2o_device remains.
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Cc: Markus Lidel <Markus.Lidel@shadowconnect.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>