libadf: silence false positive warning

Some versions of gcc warn that intfs may be used uninitialized

Change-Id: I3b8d7e919e9c2902ac56adeabd09a45ececfb3c4
Signed-off-by: Greg Hackmann <ghackmann@google.com>
diff --git a/adf/libadf/adf.c b/adf/libadf/adf.c
index 871629e..1d19152 100644
--- a/adf/libadf/adf.c
+++ b/adf/libadf/adf.c
@@ -768,7 +768,7 @@
         const __u32 *formats, size_t n_formats,
         adf_id_t *interface, adf_id_t *overlay_engine)
 {
-    adf_id_t *intfs;
+    adf_id_t *intfs = NULL;
     ssize_t n_intfs = adf_interfaces(dev, &intfs);
 
     if (n_intfs < 0)