[S390] kernel: Convert upper case scpdata to lower case

If the CP SET LOADDEV on the 3215 console has been used to specify
SCPdata, all data is converted to upper case letters.

When scpdata contains upper case letters only, convert all letters
to lower case.

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