drivers/perf: hisi: Migrate to one online CPU if no associated one online

If the selected CPU hisi_pmu::on_cpu goes offline, driver will select
a new online CPU from hisi_pmu::associated_cpus, or if no online CPU
found the PMU context won't be migrated. However for uncore PMUs the
associated CPUs are just a peference and it also works to schedule
the events on any online CPUs. So add a fallback to choose an online
CPU if no associated CPUs found.

Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
Link: https://lore.kernel.org/r/20241210141525.37788-4-yangyicong@huawei.com


Signed-off-by: Will Deacon <will@kernel.org>