mmc: mediatek: Avoid ugly error message when SDIO wakeup IRQ isn't used

When I boot a kukui-kodama board, I see an ugly warning in my kernel
log:
mtk-msdc 11240000.mmc: error -ENXIO: IRQ sdio_wakeup not found

It's pretty normal not to have an "sdio_wakeup" IRQ defined. In fact,
no device trees in mainline seem to have it. Let's use the
platform_get_irq_byname_optional() to avoid the error message.

Fixes: 527f36f5efa4 ("mmc: mediatek: add support for SDIO eint wakup IRQ")
Signed-off-by: Douglas Anderson <[e-mail]>
Reviewed-by: Matthias Brugger <[e-mail]>
Link: https://lore.kernel.org/r/20230510064434.1.I935404c5396e6bf952e99bb7ffb744c6f7fd430b@changeid
Signed-off-by: Ulf Hansson <[e-mail]>

drivers/mmc/host/mtk-sd.c

···
 
 	/* Support for SDIO eint irq ? */
 	if ((mmc->pm_caps & MMC_PM_WAKE_SDIO_IRQ) && (mmc->pm_caps & MMC_PM_KEEP_POWER)) {
-		host->eint_irq = platform_get_irq_byname(pdev, "sdio_wakeup");
+		host->eint_irq = platform_get_irq_byname_optional(pdev, "sdio_wakeup");
 		if (host->eint_irq > 0) {
 			host->pins_eint = pinctrl_lookup_state(host->pinctrl, "state_eint");
 			if (IS_ERR(host->pins_eint)) {