drm/xe/hwmon: Expose memory controller temperature

drm/xe/hwmon: Expose memory controller temperature

Expose GPU memory controller average temperature and its limits under
temp4_xxx.
Update Xe hwmon documentation for this.

v2:
 - Rephrase commit message. (Badal)
 - Update kernel version in Xe hwmon documentation. (Raag)

v3:
 - Update kernel version in Xe hwmon documentation.
 - Address review comments from Raag.
 - Remove obvious comments.
 - Remove redundant debug logs.
 - Remove unnecessary checks.
 - Avoid magic numbers.
 - Add new comments.
 - Use temperature sensors count to make memory controller visible.
 - Use temperature limits of package for memory controller.

v4:
 - Address review comments from Raag.
 - Group new temperature attributes with existing temperature attributes
   as per channel index in Xe hwmon documentation.
 - Use DIV_ROUND_UP to calculate dwords needed for temperature limits.
 - Minor aesthetic refinements.
 - Remove unused TEMP_MASK_MAILBOX.

v5:
 - Use REG_FIELD_GET to get count from READ_THERMAL_DATA output. (Raag)
 - Change count print from decimal to hexadecimal.
 - Cosmetic changes.

Signed-off-by: Karthik Poosa <karthik.poosa@intel.com>
Reviewed-by: Raag Jadav <raag.jadav@intel.com>
Link: https://patch.msgid.link/20260112203521.1014388-3-karthik.poosa@intel.com
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>