Bluetooth: controller: split: Fix Conn Param Req procedure stall issue

Fix an issue wherein local or remote initiated Connection
Parameter Request procedure would stall without generation
of LE Connection Update Complete HCI event because a local
or remote initiated PHY Update procedure has overwritten the
currently active Link Layer Control Procedure type.

Signed-off-by: Alexander Svensen <alsv@nordicsemi.no>

subsys/bluetooth/controller/ll_sw/ull_conn.c

@@ -2789,6 +2789,11 @@ static inline void event_phy_req_prep(struct ll_conn *conn)
 
 	case LLCP_PHY_STATE_UPD:
 	{
+		/* Defer if another procedure in progress */
+		if (conn->llcp_ack != conn->llcp_req) {
+			return;
+		}
+
 		/* Procedure complete */
 		conn->llcp_phy.ack = conn->llcp_phy.req;