drm/omap: Init fbdev emulation only when we have displays

Do not try to init the fbdev if either num_crtcs or num_connectors is 0.
In this case we do not have display so the fbdev init would fail anyways.

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