Fix compile warning from IAR

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/library/ccm.c b/library/ccm.c
index 6700dc7..6b137d7 100644
--- a/library/ccm.c
+++ b/library/ccm.c
@@ -91,7 +91,7 @@
     }
 #endif
 
-    return 0;
+    return ret;
 }
 
 /*