drm: omapdrm: Move PCD, LINEWIDTH and DOWNSCALE features to dispc driver

The FEAT_PARAM_DSS_PCD, FEAT_PARAM_LINEWIDTH and FEAT_PARAM_DOWNSCALE
features are specific to the DISPC, move them from the omap_dss_features
structure to the dispc driver.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>