2-Port EDD driver may call send confirmation callback twice under special conditions, even if multiple callbacks is disabled

The internal EDD architecture provides a mechanism to combine the two callbacks provided by XPEC to a single ARM callback. This is decided by the EDD_MASTER_CONFIRMATION bit which is inserted by the 2Port Switch. Under special timing conditions it is possible that this is signalled twice and the user's send callback is called twice.

This only happens under special timing conditions, which were not reproducible with in-house test setup.

This raises a fatal error inside the TCP/IP stack which results in one port not being handled anymore. After a special amount of time, it is possible that the second port also gets stuck, due to resource limits being reached (no more entries in EMPTY pointer FIFO)