tools/power/x86/intel-speed-select: Rename for_each_online_package_in_set

for_each_online_package_in_set is actually used to invoke callback for
each power domain.
This is not a problem when there is a single power domain within a
package/die, but it does not reflect the truth in multi-punit case.

Rename for_each_online_package_in_set to
for_each_online_power_domain_in_set.

Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>