cfg80211: pmsr: record netlink port ID

Without recording the netlink port ID, we cannot return the
results or complete messages to userspace, nor will we be
able to abort if the socket is closed, so clearly we need
to fill the value.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>