rcu-tasks: Fix show_rcu_tasks_trace_gp_kthread buffer overflow

In the Linux kernel, the following vulnerability has been resolved: rcu-tasks: Fix show_rcu_tasks_trace_gp_kthread buffer overflow There is a possibility of buffer overflow in show_rcu_tasks_trace_gp_kthread() if counters, passed to sprintf() are huge. Counter numbers, needed for this are unrealistically high, but buffer overflow is still possible. Use snprintf() with buffer size instead of sprintf(). Found by Linux Verification Center (linuxtesting.org) with SVACE.