lshal: arch unknown => ?

Empty strings are hard for machines to parse.
Test: lshal_test

Change-Id: I498de204c5a1829a0c2c9588a77a137336f29163
diff --git a/cmds/lshal/ListCommand.cpp b/cmds/lshal/ListCommand.cpp
index 9c77f70..c0e1a35 100644
--- a/cmds/lshal/ListCommand.cpp
+++ b/cmds/lshal/ListCommand.cpp
@@ -799,7 +799,7 @@
     mOptions.push_back({'l', "released", no_argument, v++, [](ListCommand* thiz, const char*) {
         thiz->mSelectedColumns.push_back(TableColumnType::RELEASED);
         return OK;
-    }, "print the 'is released?' column\n(Y=released, empty=unreleased or unknown)"});
+    }, "print the 'is released?' column\n(Y=released, N=unreleased, ?=unknown)"});
     mOptions.push_back({'t', "transport", no_argument, v++, [](ListCommand* thiz, const char*) {
         thiz->mSelectedColumns.push_back(TableColumnType::TRANSPORT);
         return OK;