s390/zcrypt: remove unused ancient padding code

There was some ancient code which padded the results of
a clear key ME or CRT operation with some PKCS 1.2 header.
According to the comment this was only needed by crypto
cards older than the CEX2. These cards are not supported
any more and so this patch removes this obscure result
padding code.

Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Reviewed-by: Juergen Christ <jchrist@linux.ibm.com>
Reviewed-by: Holger Dengler <dengler@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>