ARM: meson: select PINCTRL_MESON and ARCH_REQUIRE_GPIOLIB

Make sure that the Meson pinctrl driver is built whenever Meson
support is enabled.

Signed-off-by: Beniamino Galvani <b.galvani@gmail.com>
Signed-off-by: Carlo Caione <carlo@endlessm.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>