AP doesn't work at 5 GHz after upgrading hostapd from 2.10 to 2.11

[me at beroal.in.ua]

Hi. I set up my Wi-Fi USB dongle EDUP AC1200 2.4 GHz / 5 GHz (the 
Realtek RTL8812BU chipset inside, driver 
https://aur.archlinux.org/packages/rtl88x2bu-dkms-git/ ) as a Wi-Fi 
access point in the 5 GHz band. After upgrading hostapd from version 
2.10 to version 2.11 the AP stopped working. I see the AP in 
WiFiAnalyzer, but with a narrower channel (20 MHz instead of 80 MHz). 
The first smartphone sees the AP, but can't connect. The second 
smartphone see the AP, says that it uses WEP (which isn't correct), and 
asks for a password. It shouldn't ask for a password because it 
remembers the password. I can't enter my password anyway probably 
because WEP restricts its length too much. When I switch to the old 
version of hostapd, all smartphones connect without asking for a 
password. I can make the 2.11 version of hostapd work in the 2.4 GHz 
band though.

I bisected to the commit |8056b79ff1e5d746a82c2ea12011e69e99c11d3d |. 
Applying the patch below solves the problem. My `hw_mode` is `a` as you 
can see in my hostapd configuration file below.

{{{
diff --git a/src/ap/beacon.c b/src/ap/beacon.c
index ea8c88d59..408c12da8 100644
--- a/src/ap/beacon.c
+++ b/src/ap/beacon.c
@@ -90,7 +90,8 @@ static u8 * hostapd_eid_ds_params(struct hostapd_data 
*hapd, u8 *eid)
      enum hostapd_hw_mode hw_mode = hapd->iconf->hw_mode;

      if (hw_mode != HOSTAPD_MODE_IEEE80211G &&
-        hw_mode != HOSTAPD_MODE_IEEE80211B)
+        hw_mode != HOSTAPD_MODE_IEEE80211B &&
+        hw_mode != HOSTAPD_MODE_IEEE80211A)
          return eid;

      *eid++ = WLAN_EID_DS_PARAMS;
}}}

The hostapd configuration file "hostapd.conf":

{{{
interface=wifiap
driver=nl80211
logger_syslog=-1
logger_syslog_level=2
logger_stdout=-1
logger_stdout_level=2
ctrl_interface=/run/hostapd
ctrl_interface_group=0
ssid={{{skipped}}}
country_code=UA
country3=0x49
ieee80211d=1
ieee80211h=1
hw_mode=a
channel=52
beacon_int=100
dtim_period=2
max_num_sta=255
rts_threshold=-1
fragm_threshold=-1
macaddr_acl=0
auth_algs=1
ignore_broadcast_ssid=0
wmm_enabled=1
wmm_ac_bk_cwmin=4
wmm_ac_bk_cwmax=10
wmm_ac_bk_aifs=7
wmm_ac_bk_txop_limit=0
wmm_ac_bk_acm=0
wmm_ac_be_aifs=3
wmm_ac_be_cwmin=4
wmm_ac_be_cwmax=10
wmm_ac_be_txop_limit=0
wmm_ac_be_acm=0
wmm_ac_vi_aifs=2
wmm_ac_vi_cwmin=3
wmm_ac_vi_cwmax=4
wmm_ac_vi_txop_limit=94
wmm_ac_vi_acm=0
wmm_ac_vo_aifs=2
wmm_ac_vo_cwmin=2
wmm_ac_vo_cwmax=3
wmm_ac_vo_txop_limit=47
wmm_ac_vo_acm=0
ieee80211n=1
ht_capab=[HT40+][SHORT-GI-20][SHORT-GI-40]
ieee80211ac=1
vht_oper_chwidth=1
vht_oper_centr_freq_seg0_idx=58
eapol_key_index_workaround=0
eap_server=0
own_ip_addr=127.0.0.1
wpa=2
wpa_passphrase={{{skipped}}}
wpa_key_mgmt=WPA-PSK-SHA256 WPA-PSK
wpa_pairwise=CCMP
}}}