pinctrl: rockchip: Fix enable/disable/mask/unmask

The Rockchip pinctrl driver was only implementing the "mask" and
"unmask" operations though the hardware actually has two distinct
things: enable/disable and mask/unmask.  It was implementing the
"mask" operations as a hardware enable/disable and always leaving all
interrupts unmasked.

I believe that the old system had some downsides, specifically:
- (Untested) if an interrupt went off while interrupts were "masked"
  it would be lost.  Now it will be kept track of.
- If someone wanted to change an interrupt back into a GPIO (is such a
  thing sensible?) by calling irq_disable() it wouldn't actually take
  effect.  That's because Linux does some extra optimizations when
  there's no true "disable" function: it does a lazy mask.

Let's actually implement enable/disable/mask/unmask properly.

Signed-off-by: Doug Anderson <dianders@chromium.org>
Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>