mmc: core: report tuning command execution failure reason

Print the error code when the tuning command fails.  This allows the
reason for the failure to be reported, which aids debugging.
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: NUlf Hansson <ulf.hansson@linaro.org>

drivers/mmc/core/core.c

@@ -1079,7 +1079,8 @@ int mmc_execute_tuning(struct mmc_card *card)
 	err = host->ops->execute_tuning(host, opcode);
 
 	if (err)
-		pr_err("%s: tuning execution failed\n", mmc_hostname(host));
+		pr_err("%s: tuning execution failed: %d\n",
+			mmc_hostname(host), err);
 	else
 		mmc_retune_enable(host);