pinctrl: armada-37xx: add suspend/resume support

Add suspend/resume hooks in pinctrl driver to handle S2RAM operations.

Beyond the traditional register save/restore operations, these hooks
also keep the GPIOs used for both-edge IRQ synchronized between their
level (low/high) and expected IRQ polarity (falling/rising edge).

Since pinctrl is an infrastructure module, its resume should be issued
prior to other IO drivers. The pinctrl PM operations are requested at
early/late stages for this reason.

Suggested-by: Ken Ma <make@marvell.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: Gregory CLEMENT <gregory.clement@bootlin.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>