drm/tegra: Remove DRIVER_BUS_PLATFORM from driver_features

DRIVER_BUS_PLATFORM is not a DRM driver feature flag, it must not be set
in the driver's driver_features field.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>