mmc_test: only bind to supported cards

We can only perform the tests on MMC and SD cards, so avoid binding
to any other type.
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>

drivers/mmc/card/mmc_test.c

 /*
  *  linux/drivers/mmc/card/mmc_test.c
  *
- *  Copyright 2007 Pierre Ossman
+ *  Copyright 2007-2008 Pierre Ossman
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -858,6 +858,9 @@ static int mmc_test_probe(struct mmc_card *card)
 {
 	int ret;
 
+	if ((card->type != MMC_TYPE_MMC) && (card->type != MMC_TYPE_SD))
+		return -ENODEV;
+
 	mutex_init(&mmc_test_lock);
 
 	ret = device_create_file(&card->dev, &dev_attr_test);