//add this as in pure N mode, wep encryption will use software way, but there is no chance to set this as wep will not set group key in wext. WB.2008.07.08
//default using hwsec. when peer AP is in N mode only and pairwise_key_type is none_aes(which HT_IOT_ACT_PURE_N_MODE indicates it), use software security. when peer AP is in b,g,n mode mixed and pairwise_key_type is none_aes, use g mode hw security. WB on 2008.7.4