USB: Serial: symbolserial.c: remove debug module parameter

Now that all usb-serial modules are only using dev_dbg()
the debug module parameter does not do anything at all, so
remove it to reduce any confusion if someone were to try to
use it.

CC: Rusty Russell <rusty@rustcorp.com.au>
CC: Johan Hovold <jhovold@gmail.com>
CC: Alan Stern <stern@rowland.harvard.edu>
CC: Mauro Carvalho Chehab <mchehab@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/serial/symbolserial.c

@@ -20,8 +20,6 @@
 #include <linux/usb/serial.h>
 #include <linux/uaccess.h>
 
-static bool debug;
-
 static const struct usb_device_id id_table[] = {
 	{ USB_DEVICE(0x05e0, 0x0600) },
 	{ },
@@ -291,6 +289,3 @@ static struct usb_serial_driver * const serial_drivers[] = {
 module_usb_serial_driver(serial_drivers, id_table);
 
 MODULE_LICENSE("GPL");
-
-module_param(debug, bool, S_IRUGO | S_IWUSR);
-MODULE_PARM_DESC(debug, "Debug enabled or not");