powercap: intel_rapl: Use topology interface in rapl_init_domains()

It's not a good idea to access the phys_proc_id of cpuinfo directly.

Use topology_physical_package_id(cpu) instead.

Signed-off-by: Yunfeng Ye <yeyunfeng@huawei.com>
[ rjw: Changelog edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>