P2P: Avoid re-starting p2p_search in some corner cases

P2P: Avoid re-starting p2p_search in some corner cases

Search (p2p_scan) could already have been started at the point
remain-on-channel end event is being processed, e.g., if an Action frame
TX is reported immediately aftet the end of an earlier remain-on-channel
operation and the response frame is sent using an offchannel operation
while p2p_find is still in progress. Avoid trying to re-run p2p_scan
while the previous one is still running.

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