Small function declaration cleanup in slow-hash.c

- These functions are declared twice in slow-hash.c. Remove one of the copies.
- The declarations have the wrong return type, should be void, not int.

Function definitions here: 1e74586ee9/src/crypto/aesb.c (L151-L180)
Test plan: make release-test

src/crypto/slow-hash.c

@@ -47,8 +47,8 @@
 #define INIT_SIZE_BLK   8
 #define INIT_SIZE_BYTE (INIT_SIZE_BLK * AES_BLOCK_SIZE)
 
-extern int aesb_single_round(const uint8_t *in, uint8_t*out, const uint8_t *expandedKey);
-extern int aesb_pseudo_round(const uint8_t *in, uint8_t *out, const uint8_t *expandedKey);
+extern void aesb_single_round(const uint8_t *in, uint8_t *out, const uint8_t *expandedKey);
+extern void aesb_pseudo_round(const uint8_t *in, uint8_t *out, const uint8_t *expandedKey);
 
 #define VARIANT1_1(p) \
   do if (variant == 1) \
@@ -1408,9 +1408,6 @@ static void (*const extra_hashes[4])(const void *, size_t, char *) = {
   hash_extra_blake, hash_extra_groestl, hash_extra_jh, hash_extra_skein
 };
 
-extern int aesb_single_round(const uint8_t *in, uint8_t*out, const uint8_t *expandedKey);
-extern int aesb_pseudo_round(const uint8_t *in, uint8_t *out, const uint8_t *expandedKey);
-
 static size_t e2i(const uint8_t* a, size_t count) { return (*((uint64_t*)a) / AES_BLOCK_SIZE) & (count - 1); }
 
 static void mul(const uint8_t* a, const uint8_t* b, uint8_t* res) {