hostapd: allow adding initial AP without breaking STA interface connection

hostapd: allow adding initial AP without breaking STA interface connection

When switching from a STA-only configuration to AP+STA on the same phy, the
STA was previously restarted in order to notify hostapd of the new frequency,
which might not match the AP configuration.
Fix the STA restart by querying the operating frequency from within hostapd
when bringing up the AP.

Signed-off-by: Felix Fietkau <nbd@nbd.name>