Convert the Exynos5433 DECON display controller bindings to DT schema
format.

The conversion includes also updates to the bindings, matching the
current DTS and Linux driver:
1. Require "fifo" interrupt.
2. Add "dsd" as a last clock.
3. Document "power-domains" and "iommus" properties.
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220208171823.226211-5-krzysztof.kozlowski@canonical.com