hw/net: pcnet: Remove the logic of padding short frames in the receive path

Now that we have implemented unified short frames padding in the
QEMU networking codes, remove the same logic in the NIC codes.

Signed-off-by: Bin Meng <bmeng@tinylab.org>
Signed-off-by: Jason Wang <jasowang@redhat.com>
diff --git a/hw/net/pcnet.c b/hw/net/pcnet.c
index d456094..02828ae 100644
--- a/hw/net/pcnet.c
+++ b/hw/net/pcnet.c
@@ -987,7 +987,6 @@
 {
     PCNetState *s = qemu_get_nic_opaque(nc);
     int is_padr = 0, is_bcast = 0, is_ladr = 0;
-    uint8_t buf1[60];
     int remaining;
     int crc_err = 0;
     size_t size = size_;
@@ -1000,14 +999,6 @@
     printf("pcnet_receive size=%zu\n", size);
 #endif
 
-    /* if too small buffer, then expand it */
-    if (size < MIN_BUF_SIZE) {
-        memcpy(buf1, buf, size);
-        memset(buf1 + size, 0, MIN_BUF_SIZE - size);
-        buf = buf1;
-        size = MIN_BUF_SIZE;
-    }
-
     if (CSR_PROM(s)
         || (is_padr=padr_match(s, buf, size))
         || (is_bcast=padr_bcast(s, buf, size))