drm/xe/guc: add uninterruptible suspend wait for cross-process cleanup

Add a suspend_wait_blocking() exec queue op: an uninterruptible variant
of suspend_wait() for callers that must complete a suspend on behalf of a
queue that may belong to a different process than the calling task (e.g.
cleanup/undo paths). An interruptible suspend_wait() returns -ERESTARTSYS
when the calling task is signalled, which would leave the other process's
queue suspended forever - a cross-process DoS.

The blocking variant waits uninterruptibly and, on a genuine GuC timeout,
bans and tears down the queue like suspend_wait() (shared via
guc_exec_queue_suspend_timeout_ban()). It deliberately does not handle VF
recovery since a blocking caller cannot retry.

Assisted-by: Github-Copilot:Claude-opus-4.8
Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patch.msgid.link/20260713202317.2187787-11-niranjana.vishwanathapura@intel.com

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