crypt: fix the prototype of md5_sum, sha256_sum and sha512_sum

the internal sha2 hash sum functions had incorrect array size
in the prototype for the message digest argument, fixed by
using pointer so it is not misleading

src/crypt/crypt_md5.c

@@ -118,7 +118,7 @@ static void md5_init(struct md5 *s)
 	s->h[3] = 0x10325476;
 }
 
-static void md5_sum(struct md5 *s, uint8_t md[16])
+static void md5_sum(struct md5 *s, uint8_t *md)
 {
 	int i;
 

src/crypt/crypt_sha256.c

@@ -119,7 +119,7 @@ static void sha256_init(struct sha256 *s)
 	s->h[7] = 0x5be0cd19;
 }
 
-static void sha256_sum(struct sha256 *s, uint8_t md[20])
+static void sha256_sum(struct sha256 *s, uint8_t *md)
 {
 	int i;
 

src/crypt/crypt_sha512.c

@@ -136,7 +136,7 @@ static void sha512_init(struct sha512 *s)
 	s->h[7] = 0x5be0cd19137e2179ULL;
 }
 
-static void sha512_sum(struct sha512 *s, uint8_t md[20])
+static void sha512_sum(struct sha512 *s, uint8_t *md)
 {
 	int i;