pinctrl: sunxi: refactor pinctrl choice selecting for ARM64

ARM64 Allwinner SoCs used to have every pinctrl driver selected in
ARCH_SUNXI. Change this to make their default value to (ARM64 &&
ARCH_SUNXI).

Signed-off-by: Icenowy Zheng <icenowy@aosc.xyz>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>