crypto: s390 - Respect STFL bit

Bevore issuing any s390 crypto operation check whether the
CPACF facility is enabled in the facility list. That way a
virtualization layer can prevent usage of the CPACF facility
regardless of the availability of the crypto instructions.

Signed-off-by: Jan Glauber <[e-mail]>
Signed-off-by: Herbert Xu <[e-mail]>

arch/s390/crypto/crypt_s390.h

···
 	unsigned char status[16];
 	int ret;
 
+	/* check if CPACF facility (bit 17) is available */
+	if (!(stfl() & 1ULL << (31 - 17)))
+		return 0;
+
 	switch (func & CRYPT_S390_OP_MASK) {
 	case CRYPT_S390_KM:
 		ret = crypt_s390_km(KM_QUERY, &status, NULL, NULL, 0);