cpufreq: acpi-cpufreq: Clean up hot plug notifier callback
This driver has two issues. First, it tries to fiddle with the hot
plugged CPU's MSR on the UP_PREPARE event, at a time when the CPU is
not yet online. Second, the driver sets the "boost-disable" bit for a
CPU when going down, but does not clear the bit again if the CPU comes
up again due to DOWN_FAILED.
This patch fixes the issues by changing the driver to react to the
ONLINE/DOWN_FAILED events instead of UP_PREPARE. As an added benefit,
the driver also becomes symmetric with respect to the hot plug
mechanism.
Signed-off-by: Richard Cochran <rcochran@linutronix.de> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>