[realtek] Report RX error detail in debug messages

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/drivers/net/realtek.c

 		len = ( le16_to_cpu ( rx->length ) & RTL_DESC_SIZE_MASK );
 		iob_put ( iobuf, ( len - 4 /* strip CRC */ ) );
 
-		DBGC2 ( rtl, "REALTEK %p RX %d complete (length %zd)\n",
-			rtl, rx_idx, len );
-
 		/* Hand off to network stack */
 		if ( rx->flags & cpu_to_le16 ( RTL_DESC_RES ) ) {
+			DBGC ( rtl, "REALTEK %p RX %d error (length %zd, "
+			       "flags %04x)\n", rtl, rx_idx, len,
+			       le16_to_cpu ( rx->flags ) );
 			netdev_rx_err ( netdev, iobuf, -EIO );
 		} else {
+			DBGC2 ( rtl, "REALTEK %p RX %d complete (length "
+				"%zd)\n", rtl, rx_idx, len );
 			netdev_rx ( netdev, iobuf );
 		}
 		rtl->rx.cons++;