[S390] smsgiucv_app: deliver z/VM CP special messages (SMSG) as uevents

The smsgiucv_app driver registers a callback with the smsgiucv driver
to receive z/VM CP special messages (SMSG) starting with "APP".

When the callback is called for special messages, the driver creates
an uevent for the received message.  The uevent consists of additional
environment data containing the message prefix ("APP"), message sender,
and message content.

udev rules can be used to trigger application specific actions through
matching the content or sender of the special message.

Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>