iwlwifi: enable twt by default

TWT has been disabled during stabilization and further testing of the
FW code.  It is now considered stable, so TWT can be enabled in the
driver.

Signed-off-by: Golan Ben Ami <golan.ben.ami@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20200928093526.44c9093fc632.I181fc5c80988e7ecea281c60e57a22ae7ec86716@changeid


Signed-off-by: Luca Coelho <luciano.coelho@intel.com>