pinctrl: Add devm_ apis for pinctrl_{register, unregister}

Add device managed APIs devm_pinctrl_register() and
devm_pinctrl_unregister() for the APIs pinctrl_register()
and pinctrl_unregister().

This helps in reducing code in error path and sometimes
removal of .remove callback for driver unbind.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Acked-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>