Fix length(float v) issue

length(float v) just return v, so it causes length and distance(lhs, rhs) failed.

Change-Id: Ie6d85246739b9b112aecd5ab39b772ed998b12ad
Signed-off-by: lianhd <haidong@multicorewareinc.com>
diff --git a/lib/ScriptCRT/rs_cl.c b/lib/ScriptCRT/rs_cl.c
index b707f44..c84dc28 100644
--- a/lib/ScriptCRT/rs_cl.c
+++ b/lib/ScriptCRT/rs_cl.c
@@ -827,7 +827,7 @@
 }
 
 extern float __attribute__((overloadable)) length(float v) {
-    return v;
+    return fabs(v);
 }
 extern float __attribute__((overloadable)) length(float2 v) {
     return sqrt(v.x*v.x + v.y*v.y);