crypto/modes/ccm: update internal functions to const input buffers

Input buffers are not modified, so can be declared const arguments.
This will allow using `const` inputs for `modes/ccm`.

Also say `iv` const even if not required for the api update, just because it is
the case.

sys/crypto/modes/ccm.c

@@ -34,8 +34,8 @@ static inline int min(int a, int b)
     }
 }
 
-int ccm_compute_cbc_mac(cipher_t* cipher, uint8_t iv[16],
-                        uint8_t* input, size_t length, uint8_t* mac)
+int ccm_compute_cbc_mac(cipher_t* cipher, const uint8_t iv[16],
+                        const uint8_t* input, size_t length, uint8_t* mac)
 {
     uint8_t offset, block_size, mac_enc[16] = {0};
 
@@ -64,7 +64,7 @@ int ccm_compute_cbc_mac(cipher_t* cipher, uint8_t iv[16],
 
 
 int ccm_create_mac_iv(cipher_t* cipher, uint8_t auth_data_len, uint8_t M,
-                      uint8_t L, uint8_t* nonce, uint8_t nonce_len,
+                      uint8_t L, const uint8_t* nonce, uint8_t nonce_len,
                       size_t plaintext_len, uint8_t X1[16])
 {
     uint8_t M_, L_;
@@ -99,7 +99,7 @@ int ccm_create_mac_iv(cipher_t* cipher, uint8_t auth_data_len, uint8_t M,
     return 0;
 }
 
-int ccm_compute_adata_mac(cipher_t* cipher, uint8_t* auth_data,
+int ccm_compute_adata_mac(cipher_t* cipher, const uint8_t* auth_data,
                           uint32_t auth_data_len, uint8_t X1[16])
 {
     if (auth_data_len > 0) {