unreachable instruction

Noticed a problem here (line 137)
```asm
    cmp edx, 127*512
    jl loader.part_2
    jz loader.finish
```
the line `jz loader.finish` will never be executed.  It's not really a problem, it just might copy an an extra sector but not a big deal.  In any case you can either remove this instruction or get the intended functionality by moving it into the block labeled `loader.part_2`.