More standard support for the `BusComponent` interface.

Made sure that OAM DMA takes 160 cycles to process.

This is a way of controlling the bytes that have already been written by the DMA controller.

Improved some comments for DMA.

Running under a single call.
This required increasing variable size from u8 to u16.

Allows the transfer of data according to the specs in dma.rs.

This is only a structure change and no real DMA implementation has been done.