iwlwifi: mvm: avoid race condition in ADD_STA.

The race happens when we send ADD_STA(auth->assoc) -> LQ_CMD
between the commands the FW sometimes loses the medium for AUX, and
sends a ndp to the AP and the flow becomes, ADD_STA -> send ndp -> LQ_CMD
the problem is that there's no rates yet defined for sending the ndp and
FW generates an assert.

The fix: change the order of the commands to LQ_CMD -> ADD_STA

Signed-off-by: Mordechay Goodstein <mordechay.goodstein@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>