iwlwifi: pcie: add infrastructure for multiple debug buffers

In future devices we will have more than one debug buffer.
Prepare the infrastructure for allocation and release of
multiple debug buffers by grouping the variables in an array
of structures and moving it to trans section, where they will
be visible to opmode and FW.

Signed-off-by: Sara Sharon <sara.sharon@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>