PM / devfreq: rockchip-dfi: Move GRF definitions to a common place.

Some rk3399 GRF (Generic Register Files) definitions can be used for
different drivers. Move these definitions to a common include so we
don't need to duplicate these definitions.

Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Acked-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Gaël PORTAY <gael.portay@collabora.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>