[S390] cmm, smsgiucv_app: convert sender to uppercase

The sender kernel parameter contains a z/VM user ID where
alphabetic characters must be specified in uppercase.

Allow users to specify lowercase characters and convert the
sender string to uppercase at module initialization.

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