dt-bindings: soc: qcom,rpm: add missing clock-controller node

dt-bindings: soc: qcom,rpm: add missing clock-controller node

On Qualcomm platforms in addition to regulators the RPM also provides
clocks via the child clock-controller node. Describe it properly in the
schema.

Fixes: 872f91b5ea72 ("clk: qcom: Add support for RPM Clocks")
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20250318-fix-nexus-4-v2-1-bcedd1406790@oss.qualcomm.com
Signed-off-by: Bjorn Andersson <andersson@kernel.org>