crypto: xts - consolidate sanity check for keys

The patch centralizes the XTS key check logic into the service function
xts_check_key which is invoked from the different XTS implementations.
With this, the XTS implementations in ARM, ARM64, PPC and S390 have now
a sanity check for the XTS keys similar to the other arches.

In addition, this service function received a check to ensure that the
key != the tweak key which is mandated by FIPS 140-2 IG A.9. As the
check is not present in the standards defining XTS, it is only enforced
in FIPS mode of the kernel.

Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

arch/s390/crypto/aes_s390.c

@@ -587,6 +587,11 @@ static int xts_aes_set_key(struct crypto_tfm *tfm, const u8 *in_key,
 {
 	struct s390_xts_ctx *xts_ctx = crypto_tfm_ctx(tfm);
 	u32 *flags = &tfm->crt_flags;
+	int err;
+
+	err = xts_check_key(tfm, in_key, key_len);
+	if (err)
+		return err;
 
 	switch (key_len) {
 	case 32: