PM: AVS: rockchip-io: Move the driver to the rockchip specific drivers

The avs drivers are all SoC specific drivers that doesn't share any code.
Instead they are located in a directory, mostly to keep similar
functionality together. From a maintenance point of view, it makes better
sense to collect SoC specific drivers like these, into the SoC specific
directories.

Therefore, let's move the rockchip-io driver to the rockchip directory.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>