ARM: dts: Prepare for simple-pm-bus for omap4 l3

Let's configure omap4 l3 for power-domain and clocks in preparation for
starting to use simple-pm-bus. We will flip over to using simple-pm-bus
later on after dropping the legacy data for all the devices on l3
interconnect.

Signed-off-by: Tony Lindgren <tony@atomide.com>