Revert "Revert "random: make 'add_interrupt_randomness()' do something sane""

This reverts commit b6d071f2b290b06c66ede7cac45eac176c0bd252.
Revert "random: make 'add_interrupt_randomness()' do something sane"

This reverts commit 80800ef18dcd2e2a966e06493bae46331e99a704.
Build v3.85