hw/versatilepb, realview: Fix condition for instantiation of onboard NIC

Correct the condition determining whether we instantiate the onboard
NIC or a PCI card NIC on VersatilePB and Realview boards. This was broken
in two ways:
 (1) if the user asked for two default NICs ("-net nic -net nic") we would
crash trying to strcmp() a NULL pointer
 (2) if the user asked for two NICs explicitly of the same model as the
onboard NIC (eg "-net nic,model=smc91c111 -net nic,model=smc91c111")
we would try to instantiate two onboard NICs at the same address.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NAurelien Jarno <aurelien@aurel32.net>

hw/realview.c

@@ -288,8 +288,8 @@ static void realview_init(ram_addr_t ram_size,
     for(n = 0; n < nb_nics; n++) {
         nd = &nd_table[n];
 
-        if ((!nd->model && !done_nic)
-            || strcmp(nd->model, is_pb ? "lan9118" : "smc91c111") == 0) {
+        if (!done_nic && (!nd->model ||
+                    strcmp(nd->model, is_pb ? "lan9118" : "smc91c111") == 0)) {
             if (is_pb) {
                 lan9118_init(nd, 0x4e000000, pic[28]);
             } else {

hw/versatilepb.c

@@ -223,7 +223,7 @@ static void versatile_init(ram_addr_t ram_size,
     for(n = 0; n < nb_nics; n++) {
         nd = &nd_table[n];
 
-        if ((!nd->model && !done_smc) || strcmp(nd->model, "smc91c111") == 0) {
+        if (!done_smc && (!nd->model || strcmp(nd->model, "smc91c111") == 0)) {
             smc91c111_init(nd, 0x10010000, sic[25]);
             done_smc = 1;
         } else {