drm/xe/hwmon: Expose temperature limits

drm/xe/hwmon: Expose temperature limits

Read temperature limits using pcode mailbox and expose shutdown
temperature limit as tempX_emergency, critical temperature limit as
tempX_crit and GPU max temperature limit as temp2_max.

Update Xe hwmon documentation with above entries.

v2:
 - Resolve a documentation warning.
 - Address below review comments from Raag.
 - Update date and kernel version in Xe hwmon documentation.
 - Remove explicit disable of has_mbx_thermal_info for unsupported
   platforms.
 - Remove unnecessary default case in switches.
 - Remove obvious comments.
 - Use TEMP_LIMIT_MAX to compute number of dwords needed in
   xe_hwmon_thermal_info.
 - Remove THERMAL_LIMITS_DWORDS macro.
 - Use has_mbx_thermal_info for checking thermal mailbox support.

v3:
 - Address below minor comments. (Raag)
 - Group new temperature attributes with existing temperature attributes
   as per channel index in Xe hwmon documentation.
 - Rename enums of xe_temp_limit to improve clarity.
 - Use DIV_ROUND_UP to calculate dwords needed for temperature limits.
 - Use return instead of breaks in xe_hwmon_temp_read.
 - Minor aesthetic refinements.

v4:
 - Remove a redundant break. (Raag)
 - Update drm_dbg to drm_warn to inform user of unavailability for
   thermal mailbox on expected platforms.

Signed-off-by: Karthik Poosa <karthik.poosa@intel.com>
Reviewed-by: Raag Jadav <raag.jadav@intel.com>
Link: https://patch.msgid.link/20260112203521.1014388-2-karthik.poosa@intel.com
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>