configfs: remove old API

Remove the old show_attribute and store_attribute methods and update
the documentation.  Also replace the two C samples with a single new
one in the proper samples directory where people expect to find it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
diff --git a/samples/configfs/Makefile b/samples/configfs/Makefile
new file mode 100644
index 0000000..a9afd99
--- /dev/null
+++ b/samples/configfs/Makefile
@@ -0,0 +1,2 @@
+
+obj-$(CONFIG_SAMPLE_CONFIGFS) += configfs_sample.o