res_stir_shaken: Fix memory allocation error in curl.c

Fixed a memory allocation that was not passing in the correct size for
the struct in curl.c.

Change-Id: I5fb92fbbe84b075fa6aefa2423786df80e114c3a
(cherry picked from commit deaa3742)

res/res_stir_shaken/curl.c

@@ -41,7 +41,7 @@ struct curl_cb_data *curl_cb_data_create(void)
 {
 	struct curl_cb_data *data;
 
-	data = ast_calloc(1, sizeof(data));
+	data = ast_calloc(1, sizeof(*data));
 
 	return data;
 }