setprop: check if not setprop value but setprop name starts with "ro."

When setting property with setprop, a property name which starts with
"ro." could be set no matter how long the value name is.

Change-Id: Ia035ef009952db08ae8a6d4a2b8b9567d86124fc
diff --git a/toolbox/setprop.cpp b/toolbox/setprop.cpp
index acf8c3e..91edf45 100644
--- a/toolbox/setprop.cpp
+++ b/toolbox/setprop.cpp
@@ -58,7 +58,7 @@
         }
     }
 
-    if (value.size() >= PROP_VALUE_MAX && !StartsWith(value, "ro.")) {
+    if (value.size() >= PROP_VALUE_MAX && !StartsWith(name, "ro.")) {
         std::cerr << "Value '" << value << "' is too long, " << value.size()
                   << " bytes vs a max of " << PROP_VALUE_MAX << std::endl;
         return EXIT_FAILURE;