Function read

pub unsafe fn read<'a, C: Channel, W: Word>(
    ch: impl Peripheral<P = C> + 'a,
    from: *const W,
    to: *mut [W],
    dreq: TreqSel,
) -> Transfer<'a, C> 

DMA read.

SAFETY: Slice must point to a valid location reachable by DMA.