crypto: vmx - Adding asm subroutines for XTS

This patch add XTS subroutines using VMX-crypto driver.

It gives a boost of 20 times using XTS.

These code has been adopted from OpenSSL project in collaboration
with the original author (Andy Polyakov <appro@openssl.org>).
Signed-off-by: NLeonidas S. Barbosa <leosilva@linux.vnet.ibm.com>
Signed-off-by: NPaulo Flabiano Smorigo <pfsmorigo@linux.vnet.ibm.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/vmx/aesp8-ppc.h

@@ -19,3 +19,7 @@ void aes_p8_cbc_encrypt(const u8 *in, u8 *out, size_t len,
 void aes_p8_ctr32_encrypt_blocks(const u8 *in, u8 *out,
 				 size_t len, const struct aes_key *key,
 				 const u8 *iv);
+void aes_p8_xts_encrypt(const u8 *in, u8 *out, size_t len,
+			const struct aes_key *key1, const struct aes_key *key2, u8 *iv);
+void aes_p8_xts_decrypt(const u8 *in, u8 *out, size_t len,
+			const struct aes_key *key1, const struct aes_key *key2, u8 *iv);