PASN: Derive KDK only when required

When a PTK derivation is done as part of PASN authentication flow, a KDK
derivation should be done if and only if the higher layer protocol is
supported by both parties.

Fix the code accordingly, so KDK would be derived if and only if both
sides support Secure LTF.

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

src/ap/sta_info.h

@@ -88,6 +88,7 @@ struct pasn_data {
 	u16 group;
 	u8 trans_seq;
 	u8 wrapped_data_format;
+	size_t kdk_len;
 
 	u8 hash[SHA384_MAC_LEN];
 	struct wpa_ptk ptk;