iwlwifi: update channel switch command API

Channel switch host command has different data structure for
different devices. Adding additional structures to support 5000 and 6000
NICs. unlike 4965, starting with 5000 series, the tx power is managed by
uCode, there is no tx power db information need to be passing from driver to
uCode; but the space needs to be reserved to match uCode expection.

1000 NIC do not support channel switch operation since it is 'bgn'
device, there is no need to have data structure defined for it.

Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>