tools/power/x86/intel-speed-select: Improve isst_print_extended_platform_info

The main thing done in isst_print_extended_platform_info is to get the
isst feature status by checking one of the power domains of the
platform.

This can be done using the for_each_online_power_domain_in_set()
function, which makes the code clean and easier to read.

No functional changes are expected.

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