dma: move dma_ops to dma-uclass.h

Move dma_ops to a separate header file, following other uclass
implementations. While doing so, this patch also improves dma_ops
documentation.

Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
4 files changed