tests/qtest/npcm7xx_emc-test: Connect all NICs to a backend

Currently QEMU will warn if there is a NIC on the board that
is not connected to a backend. By default the '-nic user' will
get used for all NICs, but if you manually connect a specific
NIC to a specific backend, then the other NICs on the board
have no backend and will be warned about:

qemu-system-arm: warning: nic npcm7xx-emc.1 has no peer
qemu-system-arm: warning: nic npcm-gmac.0 has no peer
qemu-system-arm: warning: nic npcm-gmac.1 has no peer

So suppress those warnings by manually connecting every NIC
on the board to some backend.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-id: 20240206171231.396392-3-peter.maydell@linaro.org

tests/qtest/npcm7xx_emc-test.c

@@ -228,7 +228,10 @@ static int *packet_test_init(int module_num, GString *cmd_line)
      * KISS and use -nic. The driver accepts 'emc0' and 'emc1' as aliases
      * in the 'model' field to specify the device to match.
      */
-    g_string_append_printf(cmd_line, " -nic socket,fd=%d,model=emc%d ",
+    g_string_append_printf(cmd_line, " -nic socket,fd=%d,model=emc%d "
+                           "-nic user,model=npcm7xx-emc "
+                           "-nic user,model=npcm-gmac "
+                           "-nic user,model=npcm-gmac",
                            test_sockets[1], module_num);
 
     g_test_queue_destroy(packet_test_clear, test_sockets);