hostapd: Fix updating Beacon frames during association handling

hostapd: Fix updating Beacon frames during association handling

In function handle_assoc(), ieee802_11_update_beacons() was used to
update the Beacon frames. However, with commit a5d0bb42a226 ("Reduce
delay between Association Request and Association Response"), it was
changed to ieee802_11_set_beacons() which basically overturned what
commit e59d2a31cfb4 ("hostapd: Fix premature beacon set during
association handling") did which is not correct.

Fix this and use ieee802_11_update_beacons() instead of
ieee802_11_set_beacons().

Fixes: a5d0bb42a226 ("Reduce delay between Association Request and Association Response")
Signed-off-by: Aditya Kumar Singh <quic_adisi@quicinc.com>