arm64: dts: imx8-ss-lsio: Move lsio_bus_clk outside of soc

The lsio_bus_clk node does not have any register associated with it,
so it should be moved outside of soc to fix schema warning from
simple-bus.yaml.

Signed-off-by: Fabio Estevam <festevam@denx.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>