iwlwifi: Send DQA enable command only if TVL is on

The newer targets don't support the DQA enablement command
and will return error status, while older targets need it.
The feature is defined by the corresponding TLV.
Send the command only if the TLV is enabled.

Signed-off-by: Ilia Lin <ilia.lin@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>