If we have no beacon data before association, delay smart FIFO
enablement until after we have this data.

Not doing so can cause association failures in extremely silent
environments (usually only a shielded box/room) as beacon RX is
not sent to the host immediately, and then the association time
event ends without the host receiving any beacon even though it
was on the air - it's just stuck on the FIFO.

Cc: <stable@vger.kernel.org> [3.14]
Fixes: 1f3b0ff8 ("iwlwifi: mvm: Add Smart FIFO support")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>