mmc: core: Introduce MMC_CAP2_NO_SDIO cap

This patch introduce a new MMC_CAP2_NO_SDIO cap used to tell the mmc
core to not send SDIO specific commands.

Signed-off-by: Carlo Caione <carlo@endlessm.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 07b2f08..910aa25 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -2476,15 +2476,20 @@
 	 * sdio_reset sends CMD52 to reset card.  Since we do not know
 	 * if the card is being re-initialized, just send it.  CMD52
 	 * should be ignored by SD/eMMC cards.
+	 * Skip it if we already know that we do not support SDIO commands
 	 */
-	sdio_reset(host);
+	if (!(host->caps2 & MMC_CAP2_NO_SDIO))
+		sdio_reset(host);
+
 	mmc_go_idle(host);
 
 	mmc_send_if_cond(host, host->ocr_avail);
 
 	/* Order's important: probe SDIO, then SD, then MMC */
-	if (!mmc_attach_sdio(host))
-		return 0;
+	if (!(host->caps2 & MMC_CAP2_NO_SDIO))
+		if (!mmc_attach_sdio(host))
+			return 0;
+
 	if (!mmc_attach_sd(host))
 		return 0;
 	if (!mmc_attach_mmc(host))