Revert "cpufreq: cpu-boost: Remove unused waitqueue"

This reverts commit d06d29b9980e4ff4bdf30cbd1bfe7ede7082c6a3.
Revert "cpufreq: cpu-boost: Fix queue_delayed_work_on() race with hotplug"

This reverts commit 156fd9e4f400e9e89fb16830ffe587b6688b24f6.
Revert "cpufreq: cpu-boost: Use hotplug thread infrastructure"

This reverts commit b7e27412ef2c52540b313720738332cb63cfcd34.