dt-bindings: clock: Add "#interconnect-cells" property in IPQ9574 example

The Networking Subsystem (NSS) clock controller acts as both a clock
provider and an interconnect provider. The #interconnect-cells property
is needed in the Device Tree Source (DTS) to ensure that client drivers
such as the PPE driver can correctly acquire ICC clocks from the NSS ICC
provider.

Add the #interconnect-cells property to the IPQ9574 Device Tree binding
example to complete it.

Fixes: 28300ecedce4 ("dt-bindings: clock: Add ipq9574 NSSCC clock and reset definitions")
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Luo Jie <quic_luoj@quicinc.com>
Link: https://lore.kernel.org/r/20251014-qcom_ipq5424_nsscc-v7-2-081f4956be02@quicinc.com
Signed-off-by: Bjorn Andersson <andersson@kernel.org>