Remove duplicate function prototype

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/library/psa_crypto_cipher.h b/library/psa_crypto_cipher.h
index fae9847..e5fe23b 100644
--- a/library/psa_crypto_cipher.h
+++ b/library/psa_crypto_cipher.h
@@ -24,22 +24,6 @@
 #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       alg        PSA cipher algorithm identifier
- * \param       key_type   PSA key type
- * \param       key_bits   Size of the key in bits
- * \param[out]  cipher_id  Mbed TLS cipher algorithm identifier
- *
- * \return  The Mbed TLS cipher information of the cipher algorithm.
- *          \c NULL if the PSA cipher algorithm is not supported.
- */
-const mbedtls_cipher_info_t *mbedtls_cipher_info_from_psa(
-    psa_algorithm_t alg, psa_key_type_t key_type, size_t key_bits,
-    mbedtls_cipher_id_t *cipher_id );
-
 /**
  * \brief Set the key for a multipart symmetric encryption operation.
  *