gpio: pca953x: Restore registers after suspend/resume cycle

It is possible that the PCA953x is powered down during suspend.
Use regmap cache to assure the registers in the PCA953x are in
line with the driver state after resume.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>