Enable CONFIG_CMA_DEBUGFS

Helps with debugging of CMA related issues, or with just tracking
CMA utilization.

Change-Id: I7f87e7af0bb6406d5a999334b43ee58f5361a36f
diff --git a/debian/defconfig b/debian/defconfig
index 289e505..cc6a222 100644
--- a/debian/defconfig
+++ b/debian/defconfig
@@ -133,3 +133,4 @@
 CONFIG_YORKTOWN_TPU=m
 
 CONFIG_IMX_SDMA=m
+CONFIG_CMA_DEBUGFS=y