selftests: drv-net: psp: add tests for destroying devices

Add tests for making sure device can disappear while associations
exist. This is netdevsim-only since destroying real devices is
more tricky.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Daniel Zahka <daniel.zahka@gmail.com>
Link: https://patch.msgid.link/20250927225420.1443468-9-kuba@kernel.org
Reviewed-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

tools/testing/selftests/drivers/net/lib/py/env.py

@@ -245,6 +245,10 @@ class NetDrvEpEnv(NetDrvEnvBase):
         if not self.addr_v[ipver] or not self.remote_addr_v[ipver]:
             raise KsftSkipEx(f"Test requires IPv{ipver} connectivity")
 
+    def require_nsim(self):
+        if self._ns is None:
+            raise KsftXfailEx("Test only works on netdevsim")
+
     def _require_cmd(self, comm, key, host=None):
         cached = self._required_cmd.get(comm, {})
         if cached.get(key) is None: