drm/xe/hwmon: Expose power attributes

drm/xe/hwmon: Expose power attributes

Expose Card reactive sustained (pl1) power limit as power_max and
card default power limit (tdp) as power_rated_max.

v2:
  - Fix review comments (Riana)
v3:
  - Use drmm_mutex_init (Matt Brost)
  - Print error value (Matt Brost)
  - Convert enums to uppercase (Matt Brost)
  - Avoid extra reg read in hwmon_is_visible function (Riana)
  - Use xe_device_assert_mem_access when applicable (Matt Brost)
  - Add intel-xe@lists.freedesktop.org in Documentation (Matt Brost)
v4:
  - Use prefix xe_hwmon prefix for all functions (Matt Brost/Andi)
  - %s/hwmon_reg/xe_hwmon_reg (Andi)
  - Fix review comments (Guenter/Andi)
v5:
  - Fix review comments (Riana)
v6:
  - Use drm_warn in default case (Rodrigo)
  - s/ENODEV/EOPNOTSUPP (Andi)

Acked-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Riana Tauro <riana.tauro@intel.com>
Signed-off-by: Badal Nilawar <badal.nilawar@intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Link: https://lore.kernel.org/r/20230925081842.3566834-2-badal.nilawar@intel.com
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>