ARM: dts: Fix dm816x pinctrl and syscon so they are children of SCM

Looks like I only got half done with moving pinctrl and syscon to
be children of the SCM. I've set up the FAPLL clocks that way already,
but did not complete the job as I copied the syscon values from
am33xx.dtsi.

To make sure the syscon mapping works, I've verfified that we can
set up davinci_emac mac address the same way as cpsw already does
with the syscon mapping. So let's add that too.

Cc: Brian Hutchinson <b.hutchman@gmail.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>