Kernel prepatch 5.6-rc2

The 5.6-rc2 kernel prepatch is out fortesting. Linus says: "More than half the rc2 patch is actuallyDocumentation updates, because the kvm docs got turned into RST.Another notable chunk is just tooling updates, which is about 50/50perf updates (much of it due to header file syncing) and - again -kvm".