Staging: dgnc: Remove unused #include header file

Since the things defined by digi.h are not used in dgnc_utils.c,
remove the header from this file.
Signed-off-by: Shraddha Barke <shraddha.6596@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/dgnc/dgnc_utils.c

 #include <linux/tty.h>
 #include <linux/sched.h>
 #include "dgnc_utils.h"
-#include "digi.h"
 
 /*
  * dgnc_ms_sleep()