DPI and SDI are different from the other interfaces as they are not
hwmods and there is not platform driver for them. They could be said to
be a part of DSS or DISPC modules, although it's not a clear definition.

This patch moves DPI and SDI initialization into DSS platform driver,
making the code more consistent: omap_dss_probe() only initializes
platform drivers now.
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@ti.com>