USB: usb_serial_console: allocate fake tty and termios before calling driver open() method

The usb serial method set_termios() is called for the first time from
open() method in order to set up the termios structure with the default
device's settings, ignoring the current settings. Once it's initialized,
the next set_termios() calls will update the device with the
tty->termios settings.
Currently USB serial console code calls the driver open() method without
a tty and after that will allocate a fake tty and termios so the command
line arguments can be applied to the device
(console=ttyUSB0,115200,...). This makes the driver overwrite the
termios with the default settings and not applying the command line
options.

This patch changes usb_console_setup() to allocate the fake tty and
termios before the open() method is called.

Tested successfully with a pl2303

Signed-off-by: Aristeu Rozanski <arozansk@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>