Adf: Remove unused variable

For build-system CFLAGS clean-up.

Bug: 18632512
Change-Id: Iaacfc08aeaf1a3f27771a136f2c977e54971257b
diff --git a/adf/libadf/adf.c b/adf/libadf/adf.c
index 66c329c..c4d6681 100644
--- a/adf/libadf/adf.c
+++ b/adf/libadf/adf.c
@@ -87,7 +87,6 @@
 int adf_device_open(adf_id_t id, int flags, struct adf_device *dev)
 {
     char filename[64];
-    int err;
 
     dev->id = id;