On non-Linux, findBlkIdDevice() has unused parameters

Summary: Add Q_UNUSED() to mark the unused parameters

Test Plan: Builds with fewer warnings on FreeBSD

Differential Revision: https://phabricator.kde.org/D24155

src/core/fstab.cpp

@@ -203,6 +203,9 @@ static QString findBlkIdDevice(const char *token, const QString& value)
         rval = QString::fromLocal8Bit(c);
         free(c);
     }
+#else
+    Q_UNUSED(token);
+    Q_UNUSED(value);
 #endif
 
     return rval;