dt-bindings: clock: qcom,gcc-ipq6018: split to separate schema

The Qualcomm IPQ6018 GCC clock controller has clock inputs, thus existing
gcc-other.yaml was not describing it fully so move it to a separate schema.

Fully document the allowed and required XO and sleep clock inputs, as well
as update the provided example.

Signed-off-by: Robert Marko <robimarko@gmail.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20231026101931.695497-1-robimarko@gmail.com
Signed-off-by: Bjorn Andersson <andersson@kernel.org>