cfg80211: consider security during scan results update

AP security changes are not updated in the following scenario:
STA performs a scheduled scan on DFS channel during connection
to open AP, as some devices (wl12xx) will send a probe req on
DFS channels once activity is detected, cfg80211 gets and saves
the scan result from a probe resp. STA disconnected and AP
security is changed to AES, STA performs a passive scan,
cfg80211 gets a new scan result for the same BSSID but now from
beacon. cfg80211_bss_update() finds previous scan result from
probe resp but the security change is not updated correctly.
Fix this by considering security mismatch in rb_find_bss.

Signed-off-by: Victor Goldenshtein <victorg@ti.com>