pinctrl: imxl: Use devm_pinctrl_register() for pinctrl registration

Use devm_pinctrl_register() for pin control registration and remove
need of .remove callback.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Cc: Hongzhou Yang <hongzhou.yang@mediatek.com>
Cc: Antoine Tenart <antoine.tenart@free-electrons.com>
Cc: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>