Add driver support for DH import key and export public key

Signed-off-by: Przemek Stekiel <przemyslaw.stekiel@mobica.com>
diff --git a/library/psa_crypto_ffdh.h b/library/psa_crypto_ffdh.h
index 62b05b2..5d7d951 100644
--- a/library/psa_crypto_ffdh.h
+++ b/library/psa_crypto_ffdh.h
@@ -112,4 +112,33 @@
     size_t key_buffer_size,
     size_t *key_buffer_length);
 
+/**
+ * \brief Import DH key.
+ *
+ * \note The signature of the function is that of a PSA driver import_key
+ *       entry point.
+ *
+ * \param[in]  attributes       The attributes for the key to import.
+ * \param[in]  data             The buffer containing the key data in import
+ *                              format.
+ * \param[in]  data_length      Size of the \p data buffer in bytes.
+ * \param[out] key_buffer       The buffer containing the key data in output
+ *                              format.
+ * \param[in]  key_buffer_size  Size of the \p key_buffer buffer in bytes. This
+ *                              size is greater or equal to \p data_length.
+ * \param[out] key_buffer_length  The length of the data written in \p
+ *                                key_buffer in bytes.
+ * \param[out] bits             The key size in number of bits.
+ *
+ * \retval #PSA_SUCCESS
+ *         The key was generated successfully.
+ * \retval #PSA_ERROR_BUFFER_TOO_SMALL
+ *         The size of \p key_buffer is too small.
+ */
+psa_status_t mbedtls_psa_ffdh_import_key(
+    const psa_key_attributes_t *attributes,
+    const uint8_t *data, size_t data_length,
+    uint8_t *key_buffer, size_t key_buffer_size,
+    size_t *key_buffer_length, size_t *bits);
+
 #endif /* PSA_CRYPTO_FFDH_H */