OMAPFB: connect ovl managers to all dssdevs

OMAPFB: connect ovl managers to all dssdevs

Commit 5d89bcc341771d95e3a2996218e5949a6627f59e (OMAPDSS: remove initial
display code from omapdss) moved setting up the initial overlay, overlay
manager, output and display connections from omapdss to omapfb.

However, currently omapfb only handles the connection related to the
default display, which means that no overlay managers are connected to
other displays.

This patch changes omapfb to go through all dssdevs, and connect an
overlay manager to them.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>