mmc: mxs: fix card detection function for broken card detect

Return -ENOSYS in get_cd if broken-cd is specified in the device tree.

Commit a91fe279ae75 (mmc: mxs: use standard flag for broken card
detection) sets MMC_CAP_NEEDS_POLL when broken-cd is specified. This
driver sets this flag unconditionally as it does not support a card
detect interrupt. Instead, broken-cd means that there is no card detect
signal connected.

The mmc core checks the get_cd function return value to determine if a
card is present. Only for a non-zero return value it will attempt to
initialize the card. So retuning -ENOSYS will allow the card to be
initialized.

For comparison, mmc_gpio_get_cd in slot-gpio.c also returns -ENOSYS if
the card detect GPIO is not valid.

Signed-off-by: Daniel Willmann <[e-mail]>
Acked-by: Sascha Hauer <[e-mail]>
Signed-off-by: Ulf Hansson <[e-mail]>
Signed-off-by: Chris Ball <[e-mail]>

drivers/mmc/host/mxs-mmc.c

···
 	unsigned char			bus_width;
 	spinlock_t			lock;
 	int				sdio_irq_en;
+	bool				broken_cd;
 };
 
 static int mxs_mmc_get_cd(struct mmc_host *mmc)
···
 	struct mxs_mmc_host *host = mmc_priv(mmc);
 	struct mxs_ssp *ssp = &host->ssp;
 	int present, ret;
+
+	if (host->broken_cd)
+		return -ENOSYS;
 
 	ret = mmc_gpio_get_cd(mmc);
 	if (ret >= 0)
···
 {
 	const struct of_device_id *of_id =
 			of_match_device(mxs_mmc_dt_ids, &pdev->dev);
+	struct device_node *np = pdev->dev.of_node;
 	struct mxs_mmc_host *host;
 	struct mmc_host *mmc;
 	struct resource *iores;
···
 	mmc->ops = &mxs_mmc_ops;
 	mmc->caps = MMC_CAP_SD_HIGHSPEED | MMC_CAP_MMC_HIGHSPEED |
 		    MMC_CAP_SDIO_IRQ | MMC_CAP_NEEDS_POLL;
+
+	host->broken_cd = of_property_read_bool(np, "broken-cd");
 
 	mmc->f_min = 400000;
 	mmc->f_max = 288000000;