hurd tiocflush: Fix fix.

debian/patches/hurd-i386/git-tiocflush.diff

@@ -20,8 +20,8 @@ index 662e8ee919..0d5bc176d1 100644
  	  void *argptr = arg;
 +	  int zero = 0;
 +
-+	  if (request == TIOCFLUSH && !arg)
-+	    arg = &zero;
++	  if (request == TIOCFLUSH && !argptr)
++	    argptr = &zero;
  
  	  /* Pack an argument into the message buffer.  */
  	  void in (unsigned int count, enum __ioctl_datum type)