P2P: Fix D-Bus persistent parameter in group started event

P2P: Fix D-Bus persistent parameter in group started event

wpas_p2p_persistent_group() returns non-zero for persistent groups. This
value happens to be 2 instead of 1 due to the
P2P_GROUP_CAPAB_PERSISTENT_GROUP value. This ended up with D-Bus code
trying to encode 2 as a DBUS_TYPE_BOOLEAN value which results in an
assert from the library. Fix this by modifying
wpas_p2p_persistent_group() to return 0 or 1 instead of 0 or an
arbitrary non-zero.

Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>