OMAPDSS: SDI: fix output port_num

After the commit ef691ff4 (OMAPDSS: DT: Get source endpoint by
matching reg-id) we look for the SDI output using the port number.
However, the SDI driver doesn't set the port number, which causes the
SDI display to not initialize.

Fix this by setting the SDI port number to 1. We use a hardcoded value,
as SDI was used only on OMAP3 and it's always port number 1 there.

Reported-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Reported-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>