drm/omap: Don't call .detect() operation recursively

Instead of calling the .detect() operation recursively from the display
device back to the first device that provides hot plug detection
support, iterate over the devices manually in the DRM connector
.detect() implementation. This moves the complexity to a single central
location and simplifies the logic in omap_dss_device drivers.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>