mailbox: pcc: Refactor all PCC channel information into a structure

Currently all the PCC channel specific information are stored/maintained
in global individual arrays for each of those information. It is not
scalable and not clean if we have to stash more channel specific
information. Couple of reasons to stash more information are to extend
the support to Type 3/4 PCCT subspace and also to avoid accessing the
PCCT table entries themselves each time we need the information.

This patch moves all those PCC channel specific information into a
separate structure pcc_chan_info.

Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>