OMAPDSS: HACK: look for regulators with omap4 names

Normally the omapdss driver gets the regulators using the regulator
names assigned for omapdss. However, in an effort to get a minimal DSS
support for DT enabled kernel on selected boards, we will add omapdss
devices and platform data the old way even for DT kernel. This causes
the problem that omapdss cannot find the regulators using omapdss's
regulator names.

This patch creates a temporary workaround for DSI and HDMI by trying to
get the regulators also using native OMAP4 regulator names.

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