ARM: dts: am3517-evm: Add 'vdd_io_reg' regulator references

There are a few peripherals that generate some extra noise when they
don't have a regulator assigned to them.  This patch assigns them to
their actual tps65023 regulator 'vdd_io_reg' (VDCDC2).

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>