drm/xe/hwmon: Add SW clamp for power limits writes

drm/xe/hwmon: Add SW clamp for power limits writes

[ Upstream commit 55d49f06162e45686399df4ae6292167f0deab7c ]

Clamp writes to power limits powerX_crit/currX_crit, powerX_cap,
powerX_max, to the maximum supported by the pcode mailbox
when sysfs-provided values exceed this limit.
Although the pcode already performs clamping, values beyond the pcode
mailbox's supported range get truncated, leading to incorrect
critical power settings.
This patch ensures proper clamping to prevent such truncation.

v2:
 - Address below review comments. (Riana)
 - Split comments into multiple sentences.
 - Use local variables for readability.
 - Add a debug log.
 - Use u64 instead of unsigned long.

v3:
 - Change drm_dbg logs to drm_info. (Badal)

v4:
 - Rephrase the drm_info log. (Rodrigo, Riana)
 - Rename variable max_mbx_power_limit to max_supp_power_limit, as
   limit is same for platforms with and without mailbox power limit
   support.

Signed-off-by: Karthik Poosa <karthik.poosa@intel.com>
Fixes: 92d44a422d0d ("drm/xe/hwmon: Expose card reactive critical power")
Fixes: fb1b70607f73 ("drm/xe/hwmon: Expose power attributes")
Reviewed-by: Riana Tauro <riana.tauro@intel.com>
Link: https://lore.kernel.org/r/20250808185310.3466529-1-karthik.poosa@intel.com
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
(cherry picked from commit d301eb950da59f962bafe874cf5eb6d61a85b2c2)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>