Use bool value in set_cpu_online()

The declaration of set_cpu_online() takes a bool value. So replace
int here to make it consistent with the declaration.

Signed-off-by: Zhao Ke <ke.zhao@shingroup.cn>
Reviewed-by: Charlie Jenkins <charlie@rivosinc.com>
Link: https://lore.kernel.org/r/20240318065404.123668-1-ke.zhao@shingroup.cn


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