drm/xe: Add timeslice duration engine property to sysfs

Timeslices between multiple context is supported via
guc scheduling. Add sysfs entry to provide user defined
timeslice duration to guc scheduling.

The timeslice duration can be adjusted per-engine class using,

/sys/class/drm/cardX/device/tileN/gtN/engines/ccs/timeslice_duration_us

V8:
  - Rebase
V7:
  - Rebase to use s/xe_engine/xe_hw_engine/ - Matt
V6:
  - Remove duration validation, not relevant - Niranjana
V5:
  - Rebase to replace hw engine with eclass interface
V4:
  - Rebase to per class engine props interface
V3:
  - Rebase
  - Update commit messge to add tile
V2:
  - Rebase

Reviewed-by: Niranjana Vishwanathapura <niranjana.vishwanathapura@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Tejas Upadhyay <tejas.upadhyay@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>