arm64: skip register_cpufreq_notifier on ACPI-based systems

On ACPI based systems where the topology is setup using the API
store_cpu_topology, at the moment we do not have necessary code
to parse cpu capacity and handle cpufreq notifier, thus
resulting in a kernel panic.

Stack:
        init_cpu_capacity_callback+0xb4/0x1c8
        notifier_call_chain+0x5c/0xa0
        __blocking_notifier_call_chain+0x58/0xa0
        blocking_notifier_call_chain+0x3c/0x50
        cpufreq_set_policy+0xe4/0x328
        cpufreq_init_policy+0x80/0x100
        cpufreq_online+0x418/0x710
        cpufreq_add_dev+0x118/0x180
        subsys_interface_register+0xa4/0xf8
        cpufreq_register_driver+0x1c0/0x298
        cppc_cpufreq_init+0xdc/0x1000 [cppc_cpufreq]
        do_one_initcall+0x5c/0x168
        do_init_module+0x64/0x1e4
        load_module+0x130c/0x14d0
        SyS_finit_module+0x108/0x120
        el0_svc_naked+0x24/0x28

Fixes: 7202bde8b7ae ("arm64: parse cpu capacity-dmips-mhz from DT")
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Prashanth Prakash <pprakash@codeaurora.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>