OMAPDSS: Create links between managers, outputs and devices

Links between DSS entities are made in dss_init_connections() when a panel
device is registered, and are removed in dss_uninit_connections() when the
device is unregistered. Modify these functions to incorporate the addition of
outputs.

The fields in omap_dss_device struct gives information on which output and
manager to connect to. The desired manager and output pointers are retrieved and
prepared to form the desired links. The output is linked to the device, and then
the manager to the output.

A helper function omapdss_get_output_from_device() is created to retrieve the
output from the display by checking it's type, and the module id in case of DSI.

Signed-off-by: Archit Taneja <archit@ti.com>