PM / AVS: rockchip-io: add io selectors and supplies for rk3368

This adds the necessary data for handling io voltage domains on the rk3368.
As interesting tidbit, the rk3368 contains two separate iodomain areas.
One in the regular General Register Files (GRF) and one in PMUGRF in the
pmu power domain.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Acked-by: Kevin Hilman <khilman@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>