arm64: dts: colibri-imx8x: Use new bracket format

Use the new bracket format as described by Rob since this seems the
format that we're heading in the future.

https://lore.kernel.org/all/CAL_JsqKqQdRZC08-BGJqTjzJZ8aWA41LHMbv0QyyVePVm0co7A@mail.gmail.com/Signed-off-by: Philippe Schenker <philippe.schenker@toradex.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>