mmc: Improve MMC_TEST config text.

The test file is created under debugfs, not sysfs. Also remove
the unnecessary default n.
Signed-off-by: Will Newton <will.newton@imgtec.com>
Reviewed-by: Chris Ball <cjb@laptop.org>
Signed-off-by: Chris Ball <cjb@laptop.org>

drivers/mmc/card/Kconfig

@@ -58,12 +58,11 @@ config SDIO_UART
 
 config MMC_TEST
 	tristate "MMC host test driver"
-	default n
 	help
 	  Development driver that performs a series of reads and writes
 	  to a memory card in order to expose certain well known bugs
 	  in host controllers. The tests are executed by writing to the
-	  "test" file in sysfs under each card. Note that whatever is
+	  "test" file in debugfs under each card. Note that whatever is
 	  on your card will be overwritten by these tests.
 
 	  This driver is only of interest to those developing or