mlxsw: pci: Reorganize 'mlxsw_pci_queue' structure

The next patch will set the driver to use NAPI for event processing. Then
tasklet mechanism will be used only for EQ. Reorganize 'mlxsw_pci_queue'
to hold EQ and CQ attributes in a union. For now, add tasklet for both EQ
and CQ. This will be changed in the next patch, as 'tasklet_struct' will be
replaced with NAPI instance.

Signed-off-by: Amit Cohen <amcohen@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>