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>