Fix normalize(float)

Change-Id: I3770812f3ff64e9a1ab44ad0e3746541252d2116
diff --git a/driver/runtime/rs_cl.c b/driver/runtime/rs_cl.c
index 83327bc..44c5bd1 100644
--- a/driver/runtime/rs_cl.c
+++ b/driver/runtime/rs_cl.c
@@ -974,7 +974,7 @@
 }
 
 extern float __attribute__((overloadable)) normalize(float v) {
-    return 1.f;
+    return (v < 0.0f) ? -1.0f : 1.0f;
 }
 extern float2 __attribute__((overloadable)) normalize(float2 v) {
     return v / length(v);