ARM: dts: Configure interconnect target module for ti816x edma

We can now probe devices with device tree only configuration using
ti-sysc interconnect target module driver. Let's configure edma for
dm816x similar to what we have for dm814x.

Let's initially keep the legacy "ti,hwmods" peroperty, it will be
removed for all ti81xx in a later patch.

Note that as we now also start using the clkctrl clock binding on
dm816x, the board specific dts files must also have compatible
"ti,dm816". This is needed for the clkctrl clocks to probe properly,
so any out of tree dts files may need to be updated accordingly.

Cc: Brian Hutchinson <b.hutchman@gmail.com>
Cc: Graeme Smecher <gsmecher@threespeedlogic.com>
Cc: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>