drm/xe/xe_sysctrl: Add System Controller mailbox communication support

drm/xe/xe_sysctrl: Add System Controller mailbox communication support

Add mailbox communication layer required for interacting with System
Controller firmware, enabling command submission and response handling.

This patch implements command/response handling logic, including error
and timeout handling.

Signed-off-by: Anoop Vijay <anoop.c.vijay@intel.com>
Reviewed-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Link: https://patch.msgid.link/20260327131837.2192929-14-anoop.c.vijay@intel.com