P2P: Fix interface remove to terminate all P2P groups
Previously, it was possible to remove the main interface and leave
behind dynamic P2P group interfaces. This would eventually result in
references freed memory, so it is not really suitable behavior. Instesd,
remove all the dynamic P2P group interfaces that were created through an
interface that is now removed.
Signed-off-by: Jouni Malinen <j@w1.fi>