drm/i915/gt: Add sysfs throttle frequency interfaces

Throttling here refers to the GT frequency being clipped. Each of
the throttle reason attributes will have a 0 or 1 value depending
upon whether there is throttling and also the specific reason for
it.

The following is a brief description of the sysfs throttle
frequency attributes added:

 - throttle_reason_status: when set indicates that there is GT
   frequency clipping.

 - throttle_reason_pl1: when set indicates that PBM PL1 (platform
   or package PL1) has caused GT frequency clipping.

 - throttle_reason_pl2: when set indicates that PBM PL2 or PL3
   (platform or package PL2 or PL3) has caused GT frequency
   clipping.

 - throttle_reason_pl4: when set indicates that PL4 or IccMax has
   caused GT frequency clipping.

 - throttle_reason_thermal: when set indicates that Thermal event
   has caused GT frequency clipping.

 - throttle_reason_prochot: when set indicates that PROCHOT# has
   caused GT frequency clipping.

 - throttle_reason_ratl: when set indicates that Running Average
   Thermal Limit has caused GT frequency clipping.

 - throttle_reason_vr_thermalert: when set indicates that Hot VR
   (any processor VR)  has caused GT frequency clipping.

 - throttle_reason_vr_tdc: when set indicates that VR TDC
   (Thermal Design Current)  has caused GT frequency clipping.

Signed-off-by: Sujaritha Sundaresan <sujaritha.sundaresan@intel.com>
Signed-off-by: Andi Shyti <andi.shyti@linux.intel.com>
Cc: Dale B Stimson <dale.b.stimson@intel.com>
Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220318233938.149744-8-andi.shyti@linux.intel.com