dt-bindings: dma: convert bcm2835-dma bindings to YAML

Convert the DT binding document for bcm2835-dma from .txt to YAML.

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230617133620.53129-3-stefan.wahren@i2se.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>