[settings] Fix setting_cmp() to handle nameless settings

setting_cmp() compares by option tag and then by name.  Empty names
will always match, which gives us a false positive.

Fix by explicitly checking for empty names.

Modified-by: Michael Brown <mcb30@etherboot.org>
Signed-off-by: Michael Brown <mcb30@etherboot.org>

src/core/settings.c

 	if ( a->tag && ( a->tag == b->tag ) )
 		return 0;
 
-	/* Otherwise, compare the names */
-	return strcmp ( a->name, b->name );
+	/* Otherwise, if the settings have names, compare them */
+	if ( a->name && b->name && a->name[0] )
+		return strcmp ( a->name, b->name );
+
+	/* Otherwise, return a non-match */
+	return ( ! 0 );
 }
 
 /******************************************************************************