colibri_t20: fix display configuration

Without this patch the following error will be shown:

stdio_add_devices: Video device failed (ret=-22)

As commit ec550770 (video: tegra: Move
to using simple-panel and pwm-backlight) states the Colibri T20 needs
updating too which this patch finally attempts doing.

Signed-off-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Acked-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Tom Warren <twarren@nvidia.com>