mem: Fix for 100% write threshold in DRAM controller
mem: Fix for 100% write threshold in DRAM controller

This patch fixes the controller when a write threshold of 100% is
used.  Earlier for 100% write threshold no data is written to memory
as writes never get triggered since this corner case is not
considered.

haowu4682/gem5,haowu4682/gem5,LingxiaoJIA/gem5,haowu4682/gem5,LingxiaoJIA/gem5,LingxiaoJIA/gem5,LingxiaoJIA/gem5,haowu4682/gem5,haowu4682/gem5,LingxiaoJIA/gem5,haowu4682/gem5,haowu4682/gem5,LingxiaoJIA/gem5,LingxiaoJIA/gem5,haowu4682/gem5,haowu4682/gem5