s390/zcrypt: simplify prep of CCA key token

The preparation of the key data struct for a CCA RSA ME
operation had some improvement to skip leading zeros
in the key's exponent. However, all supported CCA cards
nowadays support leading zeros in key tokens.

So for simplifying the CCA key preparing code, this
patch simply removes this optimization 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>