[S390] dasd: let device initialization wait for LCU setup

The first DASD that is set online for a specific logical control unit
has to do certain setup steps on the storage server to make full use
of it, for example it will enable PAV.
The features and characteristics reported by the storage server will
depend on this setup, so all other devices on the same LCU will need
to wait for the setup to be finished.

Signed-off-by: Stefan Weinhuber <wein@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>