QResource: remove unnecessary mutable markers

These are all modified by ensureInitialized() and ensureChildren(),
which are const. However, ensureInitialized() does a const_cast<> on the
object before calling non-const load(), which is where these are
modified.

Change-Id: I6979d02a7395405cbf23fffd17c992546ecbda49
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Reviewed-by: Ahmad Samir <a.samirh78@gmail.com>

src/corelib/io/qresource.cpp

@@ -282,11 +282,11 @@ public:
     QLocale locale;
     QString fileName, absoluteFilePath;
     QList<QResourceRoot *> related;
-    mutable qint64 size;
-    mutable quint64 lastModified;
-    mutable const uchar *data;
+    qint64 size;
+    quint64 lastModified;
+    const uchar *data;
     mutable QStringList children;
-    mutable quint8 compressionAlgo;
+    quint8 compressionAlgo;
     bool container;
     /* 2 or 6 padding bytes */