Fix ALU: Use out pin directly instead of internal finalout bus

- Removed invalid finalout internal bus
- Use out[0..7], out[8..15], out[15] directly for flag computation
- Fixes HDL sub-bus restriction error

02/Inc16.hdl

@@ -11,6 +11,6 @@ CHIP Inc16 {
     OUT out[16];
 
     PARTS:
-    // Add 1 using Add16
+    // out = in + 1
     Add16(a=in, b[0]=true, b[1..15]=false, out=out);
 }