wifi: mac80211: fixes in FILS discovery updates

FILS discovery configuration gets updated only if the maximum interval
is set to a non-zero value, hence there is no way to reset this value
to 0 once set. Replace the check for interval with a new flag which is
set only if the configuration should be updated.

Add similar changes for the unsolicited broadcast probe response handling.

Signed-off-by: Aloka Dixit <quic_alokad@quicinc.com>
Reviewed-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Link: https://lore.kernel.org/r/20230727174100.11721-3-quic_alokad@quicinc.com
[move NULL'ing to else branch to not have intermediate NULL visible]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>