P2P: Fix P2P-GROUP-STARTED event for p2p_connect-join

P2P: Fix P2P-GROUP-STARTED event for p2p_connect-join

Commit 50178335bff450829729c91c8af798a1d3a7b408 introduced a regression
for P2P-GROUP-STARTED event indication during p2p_connect-join when
using a separate P2P group interface. wpa_s->global->p2p_group_formation
was already set in that case to point to the group interface and this
commit changed this to point to incorrect interface. Fix this by setting
p2p_group_formation here only in case a separate group interface is not
used.

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