VFS: select function's timeout is now POSIX compliant

`select` function will now round up the timeout passed as a parameter (if any).
It  makes it POSIX compliant.

* Closes https://github.com/espressif/esp-idf/issues/7514

components/vfs/include/esp_vfs.h

@@ -1,16 +1,8 @@
-// Copyright 2015-2020 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.
+/*
+ * SPDX-FileCopyrightText: 2015-2021 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
 
 #ifndef __ESP_VFS_H__
 #define __ESP_VFS_H__
@@ -411,7 +403,8 @@ int esp_vfs_utime(const char *path, const struct utimbuf *times);
  * @param timeout   If not NULL, then points to timeval structure which
  *                  specifies the time period after which the functions should
  *                  time-out and return. If it is NULL, then the function will
- *                  not time-out.
+ *                  not time-out. Note that the timeout period is rounded up to
+ *                  the system tick and incremented by one.
  *
  * @return      The number of descriptors set in the descriptor sets, or -1
  *              when an error (specified by errno) have occurred.