Use more accurate timestamps for scan results

Use more accurate timestamps for scan results

For various P2P use cases, it is useful to have more accurate timestamp
for the peer information update. This commit improves scan result
handling by using a single timestamp that is taken immediately after
fetching the results from the driver and then using that value to
calculate the time when the driver last updated the BSS entry. In
addition, more debug information is added for P2P peer updates to be
able to clearly see how old information is being used here.

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