s390/pkey: Define protected key blob format

Define a new protected key blob format. Protected key
blobs use a type of 0x00, to be distinguished from other
CCA key blobs. CCA defines type 0x00 as NULL key blob,
but pkey will never use NULL keys anyway, so it is save
to reuse this type. Using another so far undefined type
value would introduce the risk that sometimes in the
future CCA defines this so far unassigned type for a
future key blob.

Also add defines for the key token types and versions,
and use them instead of hard coded hex values.

Signed-off-by: Ingo Franzki <ifranzki@linux.ibm.com>
Reviewed-by: Harald Freudenberger <freude@linux.ibm.com>
Reviewed-by: Hendrik Brueckner <brueckner@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>