mmc: mmc_test: Use seq_puts() in mtf_testlist_show()

The script "checkpatch.pl" pointed information out like the following.

WARNING: Prefer seq_puts to seq_printf

Thus fix the affected source code place.
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Shawn Lin <shawn.lin@rock-chips.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/core/mmc_test.c

@@ -3163,7 +3163,7 @@ static int mtf_testlist_show(struct seq_file *sf, void *data)
 
 	mutex_lock(&mmc_test_lock);
 
-	seq_printf(sf, "0:\tRun all tests\n");
+	seq_puts(sf, "0:\tRun all tests\n");
 	for (i = 0; i < ARRAY_SIZE(mmc_test_cases); i++)
 		seq_printf(sf, "%d:\t%s\n", i+1, mmc_test_cases[i].name);