pinctrl: ocelot: convert pinctrl to regmap

In order to allow external control via SPI, memory-mapped areas must be
changed to use the generic regmap interface. This is step 1, and is
followed by an implementation that allows a custom regmap.

Signed-off-by: Colin Foster <colin.foster@in-advantage.com>
Link: https://lore.kernel.org/r/20211119195928.2498441-4-colin.foster@in-advantage.com


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>