drm/xe: add a new sysfs directory for gtidle properties

1) Add a new sysfs directory under devices/gt#/ called gtidle
   to contain idle properties of GT such as name, idle_status,
   idle_residency_ms

2) Remove forcewake calls for residency counter

v2:
    - abstract using function pointers (Anshuman)
    - remove forcewake calls for residency counter
    - use device_attr (Badal)
    - move rc functions to guc_pc
    - change name to gt_idle (Rodrigo)

v3:
    - return error for drmm_add_action_or_reset
    - replace file and functions with gt_idle prefix
      to gt_idle_sysfs (Himal)
    - use enum for gt idle state
    - move multiplier to gt idle and initialize (Anshuman)
    - correct doc annotation (Rodrigo)
    - remove return variable
    - use kobj_gt instead of new gtidle kobj
    - move residency_ms to gtidle file
    - retain xe_guc_pc prefix for functions in guc_rc file (Michal)

v4:
    - fix doc errors in xe_guc_pc file
    - change u64 to u32 for reading residency counter
    - keep gtidle states generic GT_IDLE_C[0/6] (Anshuman)

v5:
    - update commit message to include removal of
      forcewake calls (Anshuman)
    - return void from sysfs initialization function and add warnings
      (Andi)

v6:
    - remove extra lines (Anshuman)

Signed-off-by: Riana Tauro <riana.tauro@intel.com>
Acked-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Anshuman Gupta <anshuman.gupta@intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>