ipr: Byte swapping for device_id attribute in sysfs

On LE system, users see the wrong device_id attribute. This patch
does necessary byte swapping for device_id attribute and works on
both of LE and BE systems.

Signed-off-by: Wen Xiong <wenxiong@linux.vnet.ibm.com>
Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: James Bottomley <JBottomley@Odin.com>