[S390] zcrypt: cope with cca restriction of cex3

The cca on the crypto adapter has a restriction in the size of the
exponent if a key with a modulus bigger than 2048 bit is used. Thus
in that case we have to avoid that the crypto device driver thinks
the adapter is defect and sets it offline. Therfore a new member for
the zcrypt_device struct called max_exp_bit_length is introduced. This
will be set the first time the cca returns the error code function
not implemented. If this is done with an adapter twice it will return
-EINVAL.

Signed-off-by: Felix Beck <felix.beck@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/crypto/zcrypt_api.h

@@ -109,6 +109,7 @@ struct zcrypt_device {
 	int request_count;		/* # current requests. */
 
 	struct ap_message reply;	/* Per-device reply structure. */
+	int max_exp_bit_length;
 };
 
 struct zcrypt_device *zcrypt_device_alloc(size_t);