dmaengine: mv_xor: switch to for_each_child_of_node_scoped()

Introduce the scoped variant of the loop to automatically release the
child node when it goes out of scope, which is more robust than the
non-scoped variant, and accounts for new early exits that could be added
in the future.

Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Link: https://lore.kernel.org/r/20241011-dma_mv_xor_of_node_put-v1-2-3c2de819f463@gmail.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>