omapdss: remove check for simpler port/endpoint binding

The support for simpler port/endpoint binding was removed in the merged version
of omapdss DT. But dss_init_ports still tries to get to an endpoint even if no
port exists. Remove this as this doesn't work.

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