s390/cio: Helper functions to read CSSID, IID, and CHID

Add helper functions to expose Channel Subsystem ID (CSSID), MIF Image Id
(IID), Channel ID (CHID) and Channel Path ID (CHPID).
These values are required by the qeth driver's exploitation of network-
address-change-notifications to determine which entries belong to this
interface.

Store the Partition identifier in System log, as this may be used to map
a Linux view to a Hardware view for debugging purpose.

Signed-off-by: Alexandra Winter <wintera@linux.ibm.com>
Reviewed-by: Vineeth Vijayan <vneethv@linux.ibm.com>
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>