psa_crypto_cipher: add mbedtls_cipher_values_from_psa()

This commit splits mbedtls_cipher_info_from_psa() in 2 parts:

- mbedtls_cipher_values_from_psa() that performs parameters' validation and
  return cipher's values

- mbedtls_cipher_info_from_psa() which then use those values to return
  the proper cipher_info pointer. Of course this depends on CIPHER_C.

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/library/psa_crypto_cipher.h b/library/psa_crypto_cipher.h
index 933092d..5ed8a77 100644
--- a/library/psa_crypto_cipher.h
+++ b/library/psa_crypto_cipher.h
@@ -24,6 +24,27 @@
 #include <mbedtls/cipher.h>
 #include <psa/crypto.h>
 
+/** Get Mbed TLS cipher information given the cipher algorithm PSA identifier
+ *  as well as the PSA type and size of the key to be used with the cipher
+ *  algorithm.
+ *
+ * \param[in]      alg          PSA cipher algorithm identifier
+ * \param[in]      key_type     PSA key type
+ * \param[in,out]  key_bits     Size of the key in bits. The value provided in input
+ *                              might be updated if necessary.
+ * \param[out]     mode         Mbed TLS cipher mode
+ * \param[out]     cipher_id    Mbed TLS cipher algorithm identifier
+ *
+ * \return  On success \c PSA_SUCCESS is returned and key_bits, mode and cipher_id
+ *          are properly updated.
+ *          \c PSA_ERROR_NOT_SUPPORTED is returned if the cipher algorithm is not
+ *          supported.
+ */
+
+psa_status_t mbedtls_cipher_values_from_psa(psa_algorithm_t alg, psa_key_type_t key_type,
+                                            size_t *key_bits, mbedtls_cipher_mode_t *mode,
+                                            mbedtls_cipher_id_t *cipher_id);
+
 #if defined(MBEDTLS_CIPHER_C)
 /** Get Mbed TLS cipher information given the cipher algorithm PSA identifier
  *  as well as the PSA type and size of the key to be used with the cipher