iwlwifi: no periodic Tx/IQ calibration for 6x00/6x50 series

For both 6x00 and 6x50 series devices, periodic Tx IQ calibration is
disabled in uCode, driver do not need to set the periodic Tx/IQ calibration
bit in calibration command.

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>