codec/rfx: removed unused queue TileQueue

Declared, created, deleted but not used:

    git grep TileQueue
    libfreerdp/codec/rfx_types.h: wQueue* TileQueue;
    libfreerdp/codec/rfx.c:       context->priv->TileQueue = Queue_New(TRUE, -1, -1);
    libfreerdp/codec/rfx.c:       Queue_Free(context->priv->TileQueue);