iwlwifi: dvm: excessive if in rs_bt_update_lq()

There is no need to check 'priv->bt_ant_couple_ok' twice in
rs_bt_update_lq(). The second check is always true. Thus, the
expression can be simplified.

Signed-off-by: Denis Efremov <efremov@linux.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>