P2P: Fix p2p_intra_bss with nl80211
The current implementation of p2p_intra_bss doesn't work since the flag
isn't propagated into the corresponding hostapd config, so AP code will
never enable AP isolation and will in fact disable it again after it had
been enabled by the P2P code.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>