Pack parameters of nsh_execute() as struct nsh_exec_param_s

1. Input redirect flags currently is hardcode, passing by arguments maybe better.
2. Only support redirect to path_name, redirect to fd is needed for pipeline.

Test
  1. Redirect in
    cat < /etc/init.d/rc.sysinit

  2. Redirect with FIFO
    mkfifo /dev/testfifo
    cat /dev/testfifo &
    ls > /dev/testfifo

  3. NSH Params
    set name `uname`
    echo $name

Signed-off-by: wangjianyu3 <wangjianyu3@xiaomi.com>

include/nshlib/nshlib.h

@@ -65,6 +65,25 @@
 #  define SCHED_NSH SCHED_FIFO
 #endif
 
+struct nsh_param_s
+{
+  /* Redirect input/output through `fd` OR `path_name`
+   *
+   * Select one:
+   * 1. Using fd_in/fd_out as oldfd for dup2() if greater than -1.
+   * 2. Using file_in/file_out as full path to the file if it is
+   *    not NULL, and oflags_in/oflags_out as flags for open().
+   */
+
+  int fd_in;
+  int fd_out;
+
+  int oflags_in;
+  int oflags_out;
+  FAR const char *file_in;
+  FAR const char *file_out;
+};
+
 /****************************************************************************
  * Public Data
  ****************************************************************************/