cpuidle: riscv-sbi: Add cpuidle_disabled() check

cpuidle: riscv-sbi: Add cpuidle_disabled() check

The consumer devices that inside the cpu/cluster power domain may register
the genpd notifier where their power domains point to the pd nodes under
'/cpus/power-domains'. If the cpuidle.off==1, the genpd notifier will fail
due to sbi_cpuidle_pd_allow_domain_state is not set. We also need the
sbi_cpuidle_cpuhp_up/down to invoke the callbacks. Therefore adding a
cpuidle_disabled() check before cpuidle_register() to address the issue.

Signed-off-by: Nick Hu <nick.hu@sifive.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20240814054434.3563453-3-nick.hu@sifive.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>