arm64: dts: colibri-imx8x: Cleanup comments

Remove unnecessary comments. The Colibri-iMX8X doesn't support FlexCAN,
and the GPU is already enabled in the SOC dtsi.

Signed-off-by: João Paulo Gonçalves <joao.goncalves@toradex.com>
Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>