thermal: intel: Enable the Directed Package-level Thermal Interrupt

Package-level thermal interrupts are broadcast to all online CPUs within a
package, even though only one CPU needs to service them. This results in
unnecessary wakeups, lock contention, and corresponding performance and
power-efficiency penalties.

When supported by hardware, a CPU requests to receive directed package-
level thermal interrupts by setting a designated bit in
IA32_THERM_INTERRUPT. The operating system must then verify that hardware
has acknowledged this request by checking a designated bit in
IA32_PACKAGE_THERM_STATUS.

Enable directed package-level thermal interrupts on one CPU per package
using the CPU hotplug infrastructure. The first CPU of a package that
comes online will handle the interrupt. If the handling CPU goes offline,
select a new CPU. Temporarily enable directed interrupts on both the
current and new CPU until hardware acknowledges the new selection, then
disable them on the outgoing CPU.

Systems without directed-interrupt support continue to broadcast the
package-level interrupt to all CPUs.

Also, add a rollback mechanism in the CPU hotplug online callback to
fall back to broadcast mode if the directed-interrupt acknowledgment fails
in any package. This is most important during boot, when all CPUs in a
package come online and would otherwise keep retrying on faulty hardware.
A complete rollback is not needed in the CPU hotplug offline callback since
at that point the hardware is known to work.

While here, update an inline comment to point to the correct volume of the
Intel Software Developer's Manual.

Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Link: https://patch.msgid.link/20260613-rneri-directed-therm-intr-v3-4-3a26d1e47fc8@linux.intel.com
[ rjw: Rebased on top of 7.2-rc2 ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

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