pinctrl: mvebu: dove: request syscon regmap for global registers

Dove pinctrl uses some global config registers to control pins.
This patch requests a syscon regmap for those registers. As this
changes DT to driver requirements, fallback to a self-registered
regmap with hardcoded resources, if the corresponding syscon DT
node is missing. Also, WARN about old DT binding usage to encourage
users to update their DTBs.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>