Changeset 15093362 in rtems

Patch from Eric Norum <eric@…> to address these issues:

1) Coalesce outgoing packet into a single mbuf when the packet is spread

over more mbufs than configured transmit buffer descriptors.

2) Add dianostic counters for successful and failed coalesce attempts.
3) Add diagnostic counter for transmit retries.

NOTE: (1) lead to deadlock and the same design based on underlying
hardware characteristics is currently also in the Sonic and
i386ex/network driver.