mmc: mediatek: add support for SDIO eint wakup IRQ

Add support for eint IRQ when MSDC is used as an SDIO host. This
feature requires SDIO device support async IRQ function. With this
feature, SDIO host can be awakened by SDIO card in suspend state,
without additional pin.

MSDC driver will time-share the SDIO DAT1 pin. During suspend, MSDC
turn off clock and switch SDIO DAT1 pin to GPIO mode. And during
resume, switch GPIO function back to DAT1 mode then turn on clock.

Some device tree property should be added or modified in MSDC node
to support SDIO eint IRQ. Pinctrls "state_eint" is mandatory. Since
this feature depends on asynchronous interrupts, "wakeup-source",
"keep-power-in-suspend" and "cap-sdio-irq" flags are necessary, and
the interrupts list should be extended(the interrupt named with
sdio_wakeup):
        &mmcX {
		...
		interrupt-names = "msdc", "sdio_wakeup";
		interrupts-extended = <...>,
                              	      <&pio xxx IRQ_TYPE_LEVEL_LOW>;
                ...
                pinctrl-names = "default", "state_uhs", "state_eint";
                ...
                pinctrl-2 = <&mmc2_pins_eint>;
                ...
                cap-sdio-irq;
		keep-power-in-suspend;
		wakeup-source;
                ...
        };

Co-developed-by: Yong Mao <yong.mao@mediatek.com>
Signed-off-by: Yong Mao <yong.mao@mediatek.com>
Reviewed-by: Chaotian Jing <chaotian.jing@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Axe Yang <axe.yang@mediatek.com>
Link: https://lore.kernel.org/r/20220726062842.18846-4-axe.yang@mediatek.com


Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>