wifi: rtl8xxxu: declare concurrent mode support for 8188f

Everything is in place now for concurrent mode, we can tell the system
that we support it.
We will allow a maximum of 2 virtual interfaces, one of them can be in
AP mode.

Signed-off-by: Martin Kaistra <martin.kaistra@linutronix.de>
Reviewed-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://msgid.link/20231222101442.626837-22-martin.kaistra@linutronix.de