s390x: initialize flic before I/O subsystems

Let's have a flic before we move on to initialize more specific
subsystems that make use of it.

Signed-off-by: Fei Li <sherrylf@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
