P2P: Store SSID of the group in p2p_group data

P2P: Store SSID of the group in p2p_group data

This can be used with P2P management operations that need to verify
whether the local device is operating a specific group based on
P2P Group ID attribute from a peer.

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