When connected 320 MHz AP, use SET_MAX_BANDWIDTH set to 160 MHz,
then GET_CU_SUB_CBW20, driver should report all 320 MHz channel
CU info, so we need record center freq2 for 320 MHz at the time
of initial connection.
Change-Id: I8b8ed049926caa31bfac3c702434b68e5f5a26ae
CRs-Fixed: 3629227