ARM: dts: am3517-som: Add TI TPS65023 regulators

This commit adds the common voltage regulators used on LogicPD's
AM3517 System-On-Modules.

Signed-off-by: Derald D. Woods <woods.technical@gmail.com>
Signed-off-by: Adam Ford <aford173@gmail.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>