dts: arm: atmel: samx7x: move SAM E70/V71 DMA header to dt-bindings

Move the Atmel SAM E70/V71 DMA PERIDs header file to
include/zephyr/dt-bindings/dma and unify it for use with the entire product
family (SAM E70/S70/V70/V71).

Signed-off-by: Henrik Brix Andersen <henrik@brixandersen.dk>