crypto: ixp4xx - Use IPAD/OPAD constant

This patch simply replace all occurrence of HMAC IPAD/OPAD value by their
define.

Signed-off-by: Corentin Labbe <clabbe.montjoie@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/ixp4xx_crypto.c

@@ -23,6 +23,7 @@
 #include <crypto/ctr.h>
 #include <crypto/des.h>
 #include <crypto/aes.h>
+#include <crypto/hmac.h>
 #include <crypto/sha.h>
 #include <crypto/algapi.h>
 #include <crypto/internal/aead.h>
@@ -90,8 +91,6 @@
 #define CTL_FLAG_PERFORM_AEAD	0x0008
 #define CTL_FLAG_MASK		0x000f
 
-#define HMAC_IPAD_VALUE   0x36
-#define HMAC_OPAD_VALUE   0x5C
 #define HMAC_PAD_BLOCKLEN SHA1_BLOCK_SIZE
 
 #define MD5_DIGEST_SIZE   16