soc: actions: Move power-domain driver to the genpd dir

To simplify with maintenance let's move the action power-domain driver to
the new genpd directory. Going forward, patches are intended to be managed
through a separate git tree, according to MAINTAINERS.

Cc: "Andreas Färber" <afaerber@suse.de>
Cc: Manivannan Sadhasivam <mani@kernel.org>
Cc: <linux-actions@lists.infradead.org>
Acked-by: Manivannan Sadhasivam <mani@kernel.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>