drm/xe/pm: Capture errors and handle them

xe_pm_init may encounter failures for various reasons, such as a failure
in initializing drmm_mutex, or when dealing with a d3cold-capable device
for vram_threshold sysfs creation and setting default threshold.
Presently, all these potential failures are disregarded.

Move d3cold.lock initialization to xe_pm_init_early and cause driver
abort if mutex initialization has failed.

For xe_pm_init failures cleanup the driver and return error code

-v2
Make mutex init cleaner (Lucas)

Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240412181211.1155732-8-himal.prasad.ghimiray@intel.com
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>