Set API version for atomics so they may be tested.

Change-Id: I81f21d979c9b1abc2f27688177820772230c5e22
diff --git a/scriptc/rs_atomic.rsh b/scriptc/rs_atomic.rsh
index fef05bb..ba847cf 100644
--- a/scriptc/rs_atomic.rsh
+++ b/scriptc/rs_atomic.rsh
@@ -177,7 +177,7 @@
 
 #endif //defined(RS_VERSION) && (RS_VERSION >= 14)
 
-#if (defined(RS_VERSION) && (RS_VERSION >= 21))
+#if (defined(RS_VERSION) && (RS_VERSION >= 20))   // TODO: api 21
 
 /**
  * Atomic add one to the value at addr.