spi: cadence-quadspi: Simplify with scoped for each OF child loop

Use scoped for_each_available_child_of_node_scoped() when iterating over
device nodes to make code a bit simpler.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://patch.msgid.link/20240814143805.98874-1-krzysztof.kozlowski@linaro.org


Signed-off-by: Mark Brown <broonie@kernel.org>