mem: clean up write buffer check in Cache::handleSnoop()
mem: clean up write buffer check in Cache::handleSnoop()

The 'if (writebacks.size)' check was redundant, because
writeBuffer.findMatches() would return false if the
writebacks list was empty.

Also renamed 'mshr' to 'wb_entry' in this context since
we are pointing at a writebuffer entry and not an MSHR
(even though it's the same C++ class).

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