dt-bindings: net: ti,k3-am654-cpts: Fix assigned-clock-parents

The schema has a typo with 'assigned-clocks-parents'. As it is not
required to list assigned clocks in bindings, just drop the assigned-clocks
property definitions to fix this

Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220120172319.1628500-1-robh@kernel.org