ARM: OMAP2+: Remove unused omapdrm platform device

The omapdrm platform device is unused, as a replacement is now
registered in the omapdss driver. Remove it.

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