Update iface->current_mode when fetching new hw_features

Update iface->current_mode when fetching new hw_features

When a CHANNEL_LIST_CHANGED event is received, memory of
iface->hw_features is freed and allocated again with
hostapd_get_hw_features(), but iface->current_mode still refer to the
original memory address, which is not correct since that memory has been
freed. This could happen in cases where the driver provides channel list
updates during the lifetime of the started BSS.

Fix this by updated iface->current_mode to point to the new array of hw
features.

Fixes: 0837863fbc62 ("AP: Handle 6 GHz AP state machine with NO_IR flags")
Signed-off-by: Jouni Malinen <quic_jouni@quicinc.com>