iwlwifi: mvm: disable beamformer unless FW supports it

Current FW is declaring support for BFER in ucode_capa.capa
but it doesn't really support it unless the new LQ_SS_PARAMS API
is supported as well. Avoid publishing BFER in our VHT caps
if FW doesn't support.

Signed-off-by: Eyal Shapira <eyalx.shapira@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>