Allow configuration of Beacon frame TX rate from hostapd.conf with
"beacon_rate=xx" option. The following format is used to set
legacy/HT/VHT beacon rates:
Legacy (CCK/OFDM rates):
beacon_rate=<legacy rate in 100 kbps>
HT:
beacon_rate=ht:<HT MCS>
VHT:
beacon_rate=vht:<VHT MCS>
Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>