P2P: Replace p2p_get_peer_info with p2p_peer_known when applicable

P2P: Replace p2p_get_peer_info with p2p_peer_known when applicable

p2p_get_peer_info() was used in multiple places just to check whether a
specific peer is known. This was not the designed use for the function,
so introduce a simpler function for that purpose to make it obvious that
the p2p_get_peer_info() function is actually used only in ctrl_iface.c.

Signed-hostap: Jouni Malinen <j@w1.fi>