dts: nxp: Remove clk-* properties from nxp,kinetis-sim nodes

These are not declared in dts/bindings/arm/nxp,kinetis-sim.yaml and do
not generate any output.

Trying to get rid of properties that appear on device tree nodes but
aren't declared in bindings.

Signed-off-by: Ulf Magnusson <Ulf.Magnusson@nordicsemi.no>