cache: don't allow dirty data in the i-cache
cache: don't allow dirty data in the i-cache

removes the optimization that forwards an exclusive copy to a requester on a
read, only for the i-cache. this optimization isn't necessary because we
typically won't be writing to the i-cache.

kaiyuanl/gem5,TUD-OS/gem5-dtu,joerocklin/gem5,austinharris/gem5-riscv,zlfben/gem5,briancoutinho0905/2dsampling,samueldotj/TeeRISC-Simulator,cancro7/gem5,HwisooSo/gemV-update,yb-kim/gemV,cancro7/gem5,TUD-OS/gem5-dtu,sobercoder/gem5,yb-kim/gemV,HwisooSo/gemV-update,markoshorro/gem5,SanchayanMaity/gem5,yb-kim/gemV,rjschof/gem5,qizenguf/MLC-STT,gedare/gem5,rallylee/gem5,yb-kim/gemV,powerjg/gem5-ci-test,gedare/gem5,kaiyuanl/gem5,SanchayanMaity/gem5,sobercoder/gem5,gedare/gem5,gem5/gem5,markoshorro/gem5,sobercoder/gem5,rallylee/gem5,aclifton/cpeg853-gem5,TUD-OS/gem5-dtu,powerjg/gem5-ci-test,powerjg/gem5-ci-test,qizenguf/MLC-STT,austinharris/gem5-riscv,aclifton/cpeg853-gem5,Weil0ng/gem5,gem5/gem5,aclifton/cpeg853-gem5,sobercoder/gem5,powerjg/gem5-ci-test,joerocklin/gem5,rjschof/gem5,markoshorro/gem5,joerocklin/gem5,austinharris/gem5-riscv,rjschof/gem5,briancoutinho0905/2dsampling,rjschof/gem5,rjschof/gem5,KuroeKurose/gem5,Weil0ng/gem5,rjschof/gem5,zlfben/gem5,KuroeKurose/gem5,qizenguf/MLC-STT,kaiyuanl/gem5,yb-kim/gemV,rallylee/gem5,briancoutinho0905/2dsampling,briancoutinho0905/2dsampling,markoshorro/gem5,KuroeKurose/gem5,zlfben/gem5,briancoutinho0905/2dsampling,powerjg/gem5-ci-test,samueldotj/TeeRISC-Simulator,gedare/gem5,kaiyuanl/gem5,KuroeKurose/gem5,samueldotj/TeeRISC-Simulator,aclifton/cpeg853-gem5,sobercoder/gem5,joerocklin/gem5,gem5/gem5,aclifton/cpeg853-gem5,Weil0ng/gem5,joerocklin/gem5,gem5/gem5,KuroeKurose/gem5,HwisooSo/gemV-update,sobercoder/gem5,samueldotj/TeeRISC-Simulator,kaiyuanl/gem5,qizenguf/MLC-STT,cancro7/gem5,cancro7/gem5,powerjg/gem5-ci-test,cancro7/gem5,SanchayanMaity/gem5,gedare/gem5,Weil0ng/gem5,markoshorro/gem5,zlfben/gem5,Weil0ng/gem5,yb-kim/gemV,gedare/gem5,austinharris/gem5-riscv,KuroeKurose/gem5,Weil0ng/gem5,HwisooSo/gemV-update,powerjg/gem5-ci-test,rallylee/gem5,KuroeKurose/gem5,rallylee/gem5,gem5/gem5,HwisooSo/gemV-update,joerocklin/gem5,austinharris/gem5-riscv,samueldotj/TeeRISC-Simulator,briancoutinho0905/2dsampling,SanchayanMaity/gem5,Weil0ng/gem5,HwisooSo/gemV-update,qizenguf/MLC-STT,markoshorro/gem5,rallylee/gem5,HwisooSo/gemV-update,zlfben/gem5,kaiyuanl/gem5,gedare/gem5,TUD-OS/gem5-dtu,zlfben/gem5,yb-kim/gemV,aclifton/cpeg853-gem5,rallylee/gem5,gem5/gem5,samueldotj/TeeRISC-Simulator,samueldotj/TeeRISC-Simulator,SanchayanMaity/gem5,briancoutinho0905/2dsampling,qizenguf/MLC-STT,gem5/gem5,qizenguf/MLC-STT,zlfben/gem5,SanchayanMaity/gem5,kaiyuanl/gem5,cancro7/gem5,yb-kim/gemV,TUD-OS/gem5-dtu,sobercoder/gem5,aclifton/cpeg853-gem5,cancro7/gem5,TUD-OS/gem5-dtu,joerocklin/gem5,TUD-OS/gem5-dtu,austinharris/gem5-riscv,joerocklin/gem5,rjschof/gem5,markoshorro/gem5,SanchayanMaity/gem5,austinharris/gem5-riscv