staging: dgnc: remove unused variable in dgnc_board

TtyRefCnt was not used anywhere in dgnc.
Signed-off-by: Daeseok Youn <daeseok.youn@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/dgnc/dgnc_driver.h

@@ -213,8 +213,6 @@ struct dgnc_board {
 	uint		dgnc_serial_major;
 	uint		dgnc_transparent_print_major;
 
-	uint		TtyRefCnt;
-
 	u16		dpatype;	/* The board "type",
 					 * as defined by DPA
 					 */