drm/xe/xe_sysctrl: Add System Controller types and device integration

drm/xe/xe_sysctrl: Add System Controller types and device integration

Add foundational type definitions for System Controller (sysctrl) support
and integrate them into the xe_device structure. Introduce a capability
flag in device descriptor and runtime information to record sysctrl
presence on supported platforms.

System Controller is a separate firmware-managed entity responsible for
selected platform-level control and coordination tasks on Intel Xe3p
discrete GPU platforms. The driver communicates with it via a mailbox
interface for delegated operations.

This commit introduces core data structures required for sysctrl support,
including MMIO region definitions, a command mutex, and state tracking
required for mailbox communication.

No functional changes. This patch provides preparatory infrastructure
for System Controller support.

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/20260327131837.2192929-10-anoop.c.vijay@intel.com