dt-bindings: clock: syscon-icst: Remove unneeded unit name

The following warnings are seen with 'make dt_binding_check':

Documentation/devicetree/bindings/clock/arm,syscon-icst.example.dts:17.16-24.11: Warning (unit_address_vs_reg): /example-0/clock@00: node has a unit name, but no reg or ranges property
Documentation/devicetree/bindings/clock/arm,syscon-icst.example.dts:17.16-24.11: Warning (unit_address_format): /example-0/clock@00: unit name should not have leading 0s

Fix them by removing the unneeded clock unit name.

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Rob Herring <robh@kernel.org>