drivers/net: delete Digital EtherWorks-3 support.

This is another one that makes sense to target for obsolescence, since
it (a)appeared pre-1995, and (b)was rather rare, and (c)did not
really have any statistically significant active linux user base.

Removing this ISA 10Mbit driver support is unlikely to be even noticed
by the user base of 3.9+ linux kernels, especially when the documentation
clearly indicates the vintage with this text:

	 "...designed to  work with all kernels > 1.1.33"

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>