[PATCH] Documentation: sched-preemption: Add a SPDX license identifier

[Quchaosheng]

The file was added without a license identifier.  Add one, matching the
other files in Documentation/scheduler/.

Suggested-by: Jonathan Corbet <corbet@xxxxxxx>
Assisted-by: LLM
Signed-off-by: Quchaosheng <quchaosheng000406@xxxxxxx>
---
 Documentation/scheduler/sched-preemption.rst | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Documentation/scheduler/sched-preemption.rst b/Documentation/scheduler/sched-preemption.rst
index bfa22559c29b..b48e53587a7a 100644
--- a/Documentation/scheduler/sched-preemption.rst
+++ b/Documentation/scheduler/sched-preemption.rst
@@ -1,3 +1,5 @@
+.. SPDX-License-Identifier: GPL-2.0
+
 =====================
 Scheduler preemption
 =====================
-- 
2.43.0