Add support for arbitrary bitmaps for TRAB's  VFD command;
allow to pass boot bitmap addresses in environment variables;
allow for zero boot delay
diff --git a/board/trab/vfd.c b/board/trab/vfd.c
index d0dcedc..e00294f 100644
--- a/board/trab/vfd.c
+++ b/board/trab/vfd.c
@@ -346,9 +346,10 @@
 				}
 			}
 		}
-		display++;
-		if (display > 3)
-			display = 0;
+		if (display > 0)
+			display--;
+		else
+			display = 3;
 	}
 }