When ESP32 operates in AP-only mode the network interface is
initialized with the STA MAC address, but the Wi-Fi hardware operates
with the AP MAC address (typically STA MAC + 1).
Some Wi-Fi clients correctly address frames to the AP MAC, causing them
to be dropped by the ethernet L2 layer with "Dropping frame, not for me"
because the interface link address doesn't match.
Fix this by updating the interface link address to the AP MAC when
enabling AP mode, and restoring the STA MAC when disabling AP mode.
Signed-off-by: Sylvio Alves <sylvio.alves@espressif.com>
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