ARM: OMAP: TI816X: add powerdomains for TI816x

This patch adds required structures for powerdomain initialization on
the ti816x. It is impossible to use omap3430 structures in order to
initialize powerdomains on ti816x, because there are big differences
between PRCM module base address offsets on these CPUs.

Signed-off-by: Aida Mynzhasova <aida.mynzhasova@skitlab.ru>
Signed-off-by: Tony Lindgren <tony@atomide.com>