pinctrl: support gpio request deferred probing

As pinctrl handles, it may be possible the pinctrl gpio ranges
are still not got registered when user call pinctrl_gpio_request.
Thus, add defer support for it too.

Signed-off-by: Dong Aisheng <dong.aisheng@linaro.org>
Acked-by: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>