P2P: Allow cross connection on the parent interface

P2P: Allow cross connection on the parent interface

Previously, any P2P capable interface was skipped in cross connection
uplink consideration. However, this ends up skipping more or less all
nl80211-based driver cases now since they mark the main interface P2P
capable. Relax this rule to allow the parent interface to be used as the
non-P2P station interface for cross connection purposes.

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