drivers/net: delete at1700 ISA 10Mbit driver

These Fujitsu MB86965 based ISA 10Mbit cards were another of the
relatively rare cards dating from the early 1990s that for one reason
or another didn't seem to get a lot of use in linux.  So we retire it
now with a reasonable degree of confidence that it won't impact anyone.

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