iwlwifi: add wimax/wifi coexist support for 6x50 series

For 6x50 series, it is wimax/wifi combo device, so driver need to enable
the wimax/wifi co-exist function and send the coexist event priority
table to uCode for operation.

The priority table will be used by uCode to determine what is the proper
action it should take when co-exist with WiMAX.
For example, when WiFi runs a scan, it must own radio exclusively, therefore
will disconnect WiMAX if WiMAX is connected.

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>