drm/xe/pm: Init pcode and restore vram on power lost

Don't init pcode and restore VRAM objects in vain.
We can rely on primary GT GUC_STATUS to detect whether
card has really lost power even when d3cold is allowed by xe.
Adding d3cold.lost_power flag to avoid pcode init and vram
restoration.
Also cleaning up the TODO code comment.

v2:
- %s/xe_guc_has_lost_power()/xe_guc_in_reset().
- Used existing gt instead of new variable. [Rodrigo]
- Added kernel-doc function comment. [Rodrigo]
- xe_guc_in_reset() return true if failed to get fw.

Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230718080703.239343-6-anshuman.gupta@intel.com


Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>