Currently hdd_medium_assess_init() and hdd_medium_assess_deinit()
are not paired with event the events eSAP_START_BSS_EVENT and
eSAP_STOP_BSS_EVENT respectively. Hence multiple call traces
can be seen for eSAP_STOP_BSS_EVENT if eSAP_START_BSS_EVENT is
not invoked from __wlan_hdd_cfg80211_start_ap or SSR sequence.
To address this issue invoke hdd_medium_assess_init()
for eSAP_START_BSS_EVENT only from hdd_hostapd_sap_event_cb
if timer is not initialized already.
Change-Id: I361e371c8b59a226fe6cae97c6f66bec46eeeb0f
CRs-Fixed: 3349485
d10945a7b3