s390/pkey: fix/harmonize internal keyblob headers

Commit 'fa6999e3 ("s390/pkey: support CCA and EP11 secure ECC
private keys")' introduced PKEY_TYPE_EP11_AES as a supplement to
PKEY_TYPE_EP11. All pkeys have an internal header/payload structure,
which is opaque to the userspace. The header structures for
PKEY_TYPE_EP11 and PKEY_TYPE_EP11_AES are nearly identical and there
is no reason, why different structures are used. In preparation to fix
the keyversion handling in the broken PKEY IOCTLs, the same header
structure is used for PKEY_TYPE_EP11 and PKEY_TYPE_EP11_AES. This
reduces the number of different code paths and increases the
readability.

Fixes: fa6999e3 ("s390/pkey: support CCA and EP11 secure ECC private keys")
Signed-off-by: Holger Dengler <dengler@linux.ibm.com>
Reviewed-by: Ingo Franzki <ifranzki@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>