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/Kconfig b/samples/Kconfig
index 224ebb4..d54f28c 100644
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -70,4 +70,10 @@
 	  Builds a sample live patch that replaces the procfs handler
 	  for /proc/cmdline to print "this has been live patched".
 
+config SAMPLE_CONFIGFS
+	tristate "Build configfs patching sample -- loadable modules only"
+	depends on CONFIGFS_FS && m
+	help
+	  Builds a sample configfs interface.
+
 endif # SAMPLES