mmc: sdhci: report error once the maximum tuning loops exhausted or timeout

The original code missed to report an error when the maximum tuning
loops exhausted or timeout, it will cause the upper layer to wrongly
think the tuning process is passed.
Signed-off-by: NDong Aisheng <b29396@freescale.com>
Acked-by: NShawn Guo <shawn.guo@linaro.org>
Signed-off-by: NChris Ball <cjb@laptop.org>

drivers/mmc/host/sdhci.c

@@ -1989,6 +1989,7 @@ static int sdhci_execute_tuning(struct mmc_host *mmc, u32 opcode)
 	if (!tuning_loop_counter || !timeout) {
 		ctrl &= ~SDHCI_CTRL_TUNED_CLK;
 		sdhci_writew(host, ctrl, SDHCI_HOST_CONTROL2);
+		err = -EIO;
 	} else {
 		if (!(ctrl & SDHCI_CTRL_TUNED_CLK)) {
 			pr_info(DRIVER_NAME ": Tuning procedure"