drivers/net: delete the 3Com 3c505/3c507 intel i825xx support

For those of us who were around in the early to mid 1990's, we
will remember that the i825xx ethernet support was not something
that was considered sufficiently vetted for 24/7 use.

Folks might be inclined to use *functional* ISA hardware on some
near expired P3 ISA machines for dedicated workhorse applications,
but the odds of using (and relying on) one of these old/experimental
drivers is essentially nil.  So lets remove them.

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