drivers: eth_dw: Port to new IP stack

The main difference to how the previous driver operates, is that this
version has zero-copy transmission.  The transmit DMA descriptor is
updated for every fragment that is transmitted from the driver.

Another difference in the transmission path is that this version won't
spin indefinitely while waiting for the DMA transfer to complete; an
arbitrary number of busy checks (20) will be performed, and then
the transmission thread will yield for as long as necessary to finish
the transfer.

These two changes should fix ZEP-472; since that issue was opened for
an older version of Zephyr with uIP, I did not bother going all the way
back to test.

This has been only tested with a Galileo board, using Shared IRQ.

Jira: ZEP-1652
Jira: ZEP-472
Signed-off-by: Leandro Pereira <[email protected]>

Author: lpereira