rockchip: rk3399: Add improved pinctrl driver.

The current pinctrl driver for the RK3399 has a range of qulity issues.
E.g. it only implements the .set_state_simple() callback, it
does not parse the available pinctrl information from the DTS
(instead uses hardcoded values), is not flexible enough to cover
devices without 'interrupt' field in the DTS (e.g. PWM),
is not written generic enough to make code reusable among other
rockchip SoCs...

This patch addresses these issues by reimplementing the whole driver
from scratch using the .set_state() callback.
The new implementation covers all featurese of the old code
(i.e. it supports pinmuxing and pullup/pulldown configuration).

This patch has been tested on a RK3399-Q7 SoM (Puma).

Signed-off-by: Christoph Muellner <christoph.muellner@theobroma-systems.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>