soc: amlogic: Move power-domain drivers to the genpd dir

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

Cc: Neil Armstrong <neil.armstrong@linaro.org>
Cc: Kevin Hilman <khilman@baylibre.com>
Cc: Jerome Brunet <jbrunet@baylibre.com>
Cc: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Cc: <linux-amlogic@lists.infradead.org>
Acked-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>