[llvm-mca] Initialize each element in vector TimelineView::UsedBuffers to a default invalid buffer descriptor. NFCI

Also change the default buffer size for UsedBuffer entries to -1 (i.e. "unknown
size"). No functional change intended.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@340830 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed