thermal: int340x: processor_thermal: Add workload type hint interface

Prior to Meteor Lake processor generation, user space can pass workload
type request to the firmware. Then firmware can optimize power based on
the indicated workload type. User space also uses workload type requests
to implement its own heuristics.

The firmware in Meteor Lake processor generation is capable of predicting
workload type without software help.

To avoid duplicate processing, add a sysfs interface allowing user space
to obtain the workload hint from the firmware instead of trying to
predict the workload type by itself.

This workload hint is passed from the firmware via MMIO offset 0x5B18 of
the processor thermal PCI device. Before workload hints can be produced by
the firmware, it needs to be configured via a mailbox command.  This
mailbox command turns ON the workload hint and it allows to program a
notification delay to control the rate of notifications.

The notification delay can be changed from user space vis sysfs.

Attribute group 'workload_hint' in sysfs is used for implementing the
workload hints interface between user space and the kernel.

It contains the following attributes:

workload_type_enable:
	Enables/disables workload type hints from the firmware.

notification_delay_ms:
	Notification delay in milliseconds.

workload_type_index:
	The current workload type index predicted by the firmware (see
	the documentation changes below for supported index values and
	their meaning).

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
[ rjw: Changelog edits, documentation edits, whitespace adjustments ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>