Add the SM8550 platform to the binding.

Link: https://lore.kernel.org/r/20230320144658.1794991-1-abel.vesa@linaro.orgSigned-off-by: Abel Vesa <abel.vesa@linaro.org>
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Johan Hovold <johan+linaro@kernel.org>