Documentation: mmc: Add the introduction for mmc-utils

This patch introduces one mmc test tools called mmc-utils, which is convenient
if someone wants to exercise and test MMC/SD devices from userspace.
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/mmc/00-INDEX

@@ -6,3 +6,5 @@ mmc-dev-parts.txt
         - info on SD and MMC device partitions
 mmc-async-req.txt
         - info on mmc asynchronous requests
+mmc-tools.txt
+	- info on mmc-utils tools

Documentation/mmc/mmc-tools.txt

+MMC tools introduction
+======================
+
+There is one MMC test tools called mmc-utils, which is maintained by Chris Ball,
+you can find it at the below public git repository:
+http://git.kernel.org/cgit/linux/kernel/git/cjb/mmc-utils.git/
+
+Functions
+=========
+
+The mmc-utils tools can do the following:
+ - Print and parse extcsd data.
+ - Determine the eMMC writeprotect status.
+ - Set the eMMC writeprotect status.
+ - Set the eMMC data sector size to 4KB by disabling emulation.
+ - Create general purpose partition.
+ - Enable the enhanced user area.
+ - Enable write reliability per partition.
+ - Print the response to STATUS_SEND (CMD13).
+ - Enable the boot partition.
+ - Set Boot Bus Conditions.
+ - Enable the eMMC BKOPS feature.
+ - Permanently enable the eMMC H/W Reset feature.
+ - Permanently disable the eMMC H/W Reset feature.
+ - Send Sanitize command.
+ - Program authentication key for the device.
+ - Counter value for the rpmb device will be read to stdout.
+ - Read from rpmb device to output.
+ - Write to rpmb device from data file.
+ - Enable the eMMC cache feature.
+ - Disable the eMMC cache feature.
+ - Print and parse CID data.
+ - Print and parse CSD data.
+ - Print and parse SCR data.