gpu: ion: check for leaks in ion_client_destroy

If an ion client is destroyed without destroying all handles created
by that client, there will be leaked buffers. Print a message if this
happens.

Change-Id: Id674f508666d506b3a9ee848adbc29435c5fe8c2
Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>
diff --git a/drivers/gpu/ion/Kconfig b/drivers/gpu/ion/Kconfig
index 5bb254b..39133b5 100644
--- a/drivers/gpu/ion/Kconfig
+++ b/drivers/gpu/ion/Kconfig
@@ -16,3 +16,12 @@
 	depends on ARCH_MSM && ION
 	help
 	  Choose this option if you wish to use ion on an MSM target.
+
+config ION_LEAK_CHECK
+	bool "Check for leaked Ion buffers (debugging)"
+	depends on ION
+	help
+	  Choose this option if you wish to enable checking for leaked
+	  ion buffers at runtime. Choosing this option will also add a
+	  debugfs node under the ion directory that can be used to
+	  enable/disable the leak checking.