resolve the issue of "the machine is dead" caused by that /dev/ttyUSB2 cann't be opened
kernel_imx/drivers/usb/serial/option.c @@-980,8+980,10@@ if(old_dcd_state&&!portdata->dcd_state){ structtty_struct*tty= tty_port_tty_get(&port->port);- if(tty&&!C_CLOCAL(tty))- tty