BL uses init framework (not NSH), so the NSH rptun command is not
available. Add rptun as an init builtin command that supports
start and stop subcommands. Also add a generic unlink builtin
command for removing device nodes.
Usage in init.bl.rc:
rptun stop /dev/rptun/corecs
unlink /dev/rptun/corecs
rptun start /dev/rptun/corecs
- rptun start/stop: open device, ioctl(RPTUNIOC_START/STOP), close
- unlink: generic command to unlink any file/device node
Signed-off-by: wangyongrong <wangyongrong@xiaomi.com>