pinctrl: Add support for PM8916 GPIO's and MPP's

Add compatible string definitions and supported pin functions.

Signed-off-by: Ivan T. Ivanov <ivan.ivanov@linaro.org>
Acked-by: Bjorn Andersson <bjorn.andersson@sonymobile.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>