iwlwifi: send cmd to uCode to configure valid tx antenna

In order for uCode to select the valid antennas for transmit, driver
need to configure the allowed tx antennas through host command.

The TX_ANT_CONFIGURATION_CMD should be used for 5000 series and up

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>