dt-bindings: dma: Add Arm DMA-350

Arm CoreLink DMA-350 is a pleasantly straightforward DMA controller
which, although highly configurable, lends itself to a simple binding
thanks to plenty of self-describing ID registers.

Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>