Don't call into the TTY layer when inside kdb.

We should just leave the underlying TTY objects alone when scrolling
around in KDB. It should be handled by Syscons exclusively.

Reported by:	pluknet gmail com

sys/dev/syscons/syscons.c

@@ -3277,7 +3277,7 @@ scgetc(sc_softc_t *sc, u_int flags)
 			    sc_draw_cursor_image(scp);
 			}
 			tp = SC_DEV(sc, scp->index);
-			if (tty_opened(tp))
+			if (!kdb_active && tty_opened(tp))
 			    sctty_outwakeup(tp);
 #endif
 		    }