drm/xe: Default auto_link_downgrade status to false

drm/xe: Default auto_link_downgrade status to false

xe_pcode_read() can return back successfully without updating the
variable 'val'. This can cause an arbitrary value to show up in the
sysfs file.

Allow the auto_link_downgrade_status to default to 0 to avoid any
arbitrary value from coming up.

Fixes: 0e414bf7ad01 ("drm/xe: Expose PCIe link downgrade attributes")
Reviewed-by: Tejas Upadhyay <tejas.upadhyay@intel.com>
Signed-off-by: Aradhya Bhatia <aradhya.bhatia@intel.com>
Link: https://lore.kernel.org/r/20250516124355.4872-1-aradhya.bhatia@intel.com
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>