dt-bindings: ata: drop unused Exynos SATA bindings

The Samsung Exynos SoC SATA bindings are not implemented in the kernel,
not used and superseded by generic
Documentation/devicetree/bindings/ata/ahci-platform.txt bindings.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20210811083859.28234-1-krzysztof.kozlowski@canonical.com


Signed-off-by: Rob Herring <robh@kernel.org>