Don't pass the async config data to async callbacks

The config data is in the SSL config, so callbacks can retrieve it
from there, with the new function mbedtls_ssl_conf_get_async_config_data.
diff --git a/library/ssl_srv.c b/library/ssl_srv.c
index 6819e7a..5439f6d 100644
--- a/library/ssl_srv.c
+++ b/library/ssl_srv.c
@@ -2847,7 +2847,7 @@
     unsigned char *sig_start = ssl->out_msg + ssl->out_msglen + 2;
     size_t sig_max_len = ( ssl->out_buf + MBEDTLS_SSL_MAX_CONTENT_LEN
                            - sig_start );
-    int ret = ssl->conf->f_async_resume( ssl->conf->p_async_config_data, ssl,
+    int ret = ssl->conf->f_async_resume( ssl,
                                          sig_start, signature_len, sig_max_len );
     if( ret != MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS )
     {
@@ -3174,8 +3174,7 @@
 #if defined(MBEDTLS_SSL_ASYNC_PRIVATE)
         if( ssl->conf->f_async_sign_start != NULL )
         {
-            ret = ssl->conf->f_async_sign_start( ssl->conf->p_async_config_data,
-                                                 ssl,
+            ret = ssl->conf->f_async_sign_start( ssl,
                                                  mbedtls_ssl_own_cert( ssl ),
                                                  md_alg, hash, hashlen );
             switch( ret )
@@ -3402,7 +3401,7 @@
                                    size_t *peer_pmslen,
                                    size_t peer_pmssize )
 {
-    int ret = ssl->conf->f_async_resume( ssl->conf->p_async_config_data, ssl,
+    int ret = ssl->conf->f_async_resume( ssl,
                                          peer_pms, peer_pmslen, peer_pmssize );
     if( ret != MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS )
     {
@@ -3465,8 +3464,7 @@
 #if defined(MBEDTLS_SSL_ASYNC_PRIVATE)
     if( ssl->conf->f_async_decrypt_start != NULL )
     {
-        ret = ssl->conf->f_async_decrypt_start( ssl->conf->p_async_config_data,
-                                                ssl,
+        ret = ssl->conf->f_async_decrypt_start( ssl,
                                                 mbedtls_ssl_own_cert( ssl ),
                                                 p, len );
         switch( ret )