USB: serial: spcp8x5: remove unused struct 'spcp8x5_usb_ctrl_arg'

'spcp8x5_usb_ctrl_arg' has been unused since the original
commit 619a6f1d ("USB: add usb-serial spcp8x5 driver").

Remove it.
Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Signed-off-by: Johan Hovold <johan@kernel.org>

drivers/usb/serial/spcp8x5.c

@@ -49,16 +49,6 @@ static const struct usb_device_id id_table[] = {
 };
 MODULE_DEVICE_TABLE(usb, id_table);
 
-struct spcp8x5_usb_ctrl_arg {
-	u8	type;
-	u8	cmd;
-	u8	cmd_type;
-	u16	value;
-	u16	index;
-	u16	length;
-};
-
-
 /* spcp8x5 spec register define */
 #define MCR_CONTROL_LINE_RTS		0x02
 #define MCR_CONTROL_LINE_DTR		0x01