[SCSI] use default attributes for scsi_host

This patch removes the unused sysfs attibute overwriting logic for
the scsi host attibutes, and plugs them into the driver core default
attribute creation.

Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>