Removed a dead while block from the PCnet code.

src/network/net_pcnet.c

@@ -1263,10 +1263,6 @@ pcnetReceiveNoSync(void *priv, uint8_t *buf, int size)
                 /* In loopback mode, Runt Packed Accept is always enabled internally;
                  * don't do any padding because guest may be looping back very short packets.
                  */
-                if (!CSR_LOOP(dev))
-                    while (size < 60)
-                        src[size++] = 0;
-
                 uint32_t fcs = UINT32_MAX;
                 uint8_t *p = src;