mfd: dt-bindings: google,cros-ec: Reference Samsung SPI bindings

mfd: dt-bindings: google,cros-ec: Reference Samsung SPI bindings

The ChromeOS Embedded Controller appears on boards with Samsung Exynos
SoC, where Exynos SPI bindings expect controller-data node.  Reference
SPI peripheral bindings which include now Samsung SPI peripheral parts.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20220124082347.32747-3-krzysztof.kozlowski@canonical.com