rcutorture: Fix rcutorture_one_extend_check() splat in RT kernels

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CVE-2025-39745

In the Linux kernel, the following vulnerability has been resolved: rcutorture: Fix rcutortureoneextendcheck splat in RT kernels For built with CONFIGPREEMPTRT=y kernels, running rcutorture tests resulted in the following splat: 68.797425 rcutortureoneextendcheck during change: Current 0x1 To add...