[PATCH] USB: drivers/serial/usb-serial: Remove unneeded void * casts

The following patch removes unneeded casts for the following (void *) pointers:
	- tty_struct->driver_data
	- void *private argument of usb_serial_port_softint()

Signed-off-by: Tobias Klauser <tklauser@nuerscht.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>