tx_bitrate is used as indication of macThroughputCapacity in transmitter link metric for backhaul STA link. tx_bitrate is added in wlan_node_info structure and os_if interface is exposed so that SON module could get the tx_bitrate parameter. Change-Id: Ib9949906b3247519bf8c1ce786d6b93d38d4d8ea CRs-Fixed: 3154548