thermal: netlink: Add a new event to notify CPU capabilities change

Add a new netlink event to notify change in CPU capabilities in terms of
performance and efficiency.

Firmware may change CPU capabilities as a result of thermal events in the
system or to account for changes in the TDP (thermal design power) level.

This notification type will allow user space to avoid running workloads
on certain CPUs or proactively adjust power limits to avoid future events.

The netlink message consists of a nested attribute
(THERMAL_GENL_ATTR_CPU_CAPABILITY) with three attributes:

 * THERMAL_GENL_ATTR_CPU_CAPABILITY_ID (type u32):
   -- logical CPU number
 * THERMAL_GENL_ATTR_CPU_CAPABILITY_PERFORMANCE (type u32):
   -- Scaled performance from 0-1023
 * THERMAL_GENL_ATTR_CPU_CAPABILITY_EFFICIENCY (type u32):
   -- Scaled efficiency from 0-1023

Reviewed-by: Len Brown <len.brown@intel.com>
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>