s390/sysinfo: add and display licensed internal code identifier

With z14, the store system information instruction provides an
licensed internal code identifier.  Display it in /proc/sysinfo.

For more information, see the z/Architecture Principles of Operation.
(SA22-7832-11).

Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>