colibri-imx8qxp: rename all occurences to colibri-imx8x

The Toradex product is called colibri-imx8x consisting of SoM with
i.MX8QXP and i.MX8DX SoCs.

Signed-off-by: Philippe Schenker <philippe.schenker@toradex.com>
Reviewed-by: Igor Opaniuk <igor.opaniuk@toradex.com>