drivers: perf: Fix smp_processor_id() use in preemptible code

As reported in [1], the use of smp_processor_id() in
pmu_sbi_device_probe() must be protected by disabling the preemption, so
simple use get_cpu()/put_cpu() instead.

Reported-by: Nam Cao <namcao@linutronix.de>
Closes: https://lore.kernel.org/linux-riscv/20240820074925.ReMKUPP3@linutronix.de/

 [1]
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Tested-by: Nam Cao <namcao@linutronix.de>
Fixes: a8625217 ("drivers/perf: riscv: Implement SBI PMU snapshot function")
Reported-by: Andrea Parri <parri.andrea@gmail.com>
Tested-by: Andrea Parri <parri.andrea@gmail.com>
Link: https://lore.kernel.org/r/20240826165210.124696-1-alexghiti@rivosinc.com


Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>