[S390]: Rewrite of the IUCV base code, part 2

Add rewritten IUCV base code to net/iucv.

Signed-off-by: Frank Pavlic <fpavlic@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>