drm: omapdrm: hdmi: Store PHY features in PHY data structure

PHY features are stored in a global variable, while they should be
properties of the PHY object. As existing OMAP platforms have a single
HDMI PHY this doesn't cause any issue, but doesn't follow the driver
model.

Move the PHY features to the HDMI PHY data structure to follow the
driver model and pave the road for multiple HDMI PHYs support.

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