Fix the disk_write logic error (#3693)

This is indeed a logic error, but actually it does not take effect so it does not cause any install/update failure.

Ventoy2Disk/Ventoy2Disk/ff14/source/diskio.c

@@ -228,6 +228,7 @@ DRESULT disk_write (
             return RES_OK;
         }
 
+        buff += 512;
         sector++;
         count--;
     }