hostapd: Fix CHAN_SWITCH command for VHT20 and VHT40

hostapd: Fix CHAN_SWITCH command for VHT20 and VHT40

Previously, hostapd CHAN_SWITCH command did not effect VHT configuration
for the following:

When VHT is currently disabled (ieee80211ac=0),

1. hostapd_cli -p /var/run/hostapd chan_switch 10 5180 \
                sec_channel_offset=1 center_freq1=5190 bandwidth=40 ht

====> Comes up in HT40

2. hostapd_cli -p /var/run/hostapd chan_switch 10 5765 \
                sec_channel_offset=-1 center_freq1=5775 bandwidth=40 vht

====> Comes up in HT40

3. hostapd_cli -p /var/run/hostapd chan_switch 10 5200 center_freq1=5200 \
                                                  bandwidth=20 vht

====> Comes up in HT20

When VHT is currently enabled (ieee80211ac=1),

1. hostapd_cli -p /var/run/hostapd chan_switch 10 5180 \
                sec_channel_offset=1 center_freq1=5190 bandwidth=40 ht

====> Comes up in VHT40

2. hostapd_cli -p /var/run/hostapd chan_switch 10 5200 center_freq1=5200 \
                                                  bandwidth=20 ht

====> Comes up in VHT20

This is since VHT config from chan_switch is processed only for
bandwidths 80 and above (80P80, 160) and for VHT20, VHT40 cases, only
NLA chan type and chan width are updated.

There is no NL attribute for determining if it is HT or VHT for
bandwidths 20 & 40 and currently they are updated as HT20, HT40 (+ or -
depending on offset). Same is notified back via
NL80211_CMD_CH_SWITCH_NOTIFY.

Instead of adding new NL attribute for tracking HT/VHT enabled config,
we are adding new hostapd VHT config parameter to save the chan_switch
config and use only for chan_switch case of VHT20 and VHT40.

Tested with all combinations of chan_switch (noHT->20->40->80->) HT/VHT
and confirmed to be working.

Signed-off-by: Sathishkumar Muruganandam <murugana@codeaurora.org>