Allow method override

Remove final keyword to allow inheritance.

Author: Arto Kinnunen

connectivity/nanostack/mbed-mesh-api/mbed-mesh-api/MeshInterfaceNanostack.h

@@ -26,8 +26,8 @@
 class Nanostack::Interface : public OnboardNetworkStack::Interface, private mbed::NonCopyable<Nanostack::Interface> {
 public:
     nsapi_error_t get_ip_address(SocketAddress *address) final;
-    char *get_mac_address(char *buf, nsapi_size_t buflen) final;
-    nsapi_error_t set_mac_address(uint8_t *buf, nsapi_size_t buflen) final;
+    char *get_mac_address(char *buf, nsapi_size_t buflen);
+    nsapi_error_t set_mac_address(uint8_t *buf, nsapi_size_t buflen);
     nsapi_error_t get_netmask(SocketAddress *address) final;
     nsapi_error_t get_gateway(SocketAddress *address) override;
     void attach(mbed::Callback<void(nsapi_event_t, intptr_t)> status_cb) final;