drm/xe: Add frequency throttle reasons sysfs attributes

Add throttle reasons sysfs attributes under a separate directory.

/device/tile<n>/gt<n>/freq0/throttle
			|- reason_pl1
			|- reason_pl2
			|- reason_pl4
			|- reason_prochot
			|- reason_ratl
			|- reason_vr_tdc
			|- reason_vr_thermalert
			|- status

v2: Remove unnecessary headers and clean-up action (Riana)

Signed-off-by: Sujaritha Sundaresan <sujaritha.sundaresan@intel.com>
Reviewed-by: Riana Tauro <riana.tauro@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>