VFS: Implement pread() and pwrite()

Closes https://github.com/espressif/esp-idf/issues/3515

components/newlib/pread.c

@@ -0,0 +1,21 @@
+// Copyright 2019 Espressif Systems (Shanghai) PTE LTD
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <unistd.h>
+#include "esp_vfs.h"
+
+ssize_t pread(int fd, void *dst, size_t size, off_t offset)
+{
+    return esp_vfs_pread(fd, dst, size, offset);
+}