P2PS: Re-factor p2ps_group_capability()

P2PS: Re-factor p2ps_group_capability()

The code was iterating all the interfaces, and for each interface
iterated all the network blocks to count active P2P GO and P2P Client
interfaces.

Change the code to reuse wpas_p2p_get_go_group() to get a P2P GO
interface and add wpas_p2p_get_cli_group() and use it to find a
P2P Client interface, and use these objects when evaluating the
group capability.

Signed-off-by: Ilan Peer <ilan.peer@intel.com>