ACPI / CPPC: move all PCC related information into pcc_data

There are several global variables in cppc driver that are related
to PCC channel used for CPPC. This patch collects all such
information into a single consolidated structure(cppc_pcc_data).
Signed-off-by: Prashanth Prakash <pprakash@codeaurora.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>