The OMAP driver has its own OF graph helpers that are similar to the
common helpers. This commit replaces most of the calls with the common
helpers. There's still a couple of custom helpers left, but the driver
needs more extensive changes to get rid of them.

In dss_init_ports, we invert the loop, looping through the known ports
and matching them to DT nodes rather than looping thru DT nodes and
matching them to the ports.
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sean Paul <seanpaul@chromium.org>