net: intel: remove dead links

The Kconfig for Intel NICs references two different URLs for the "Adapter
& Driver ID Guide". Neither of those two links works. The current URL seems
to be
http://www.intel.com/content/www/us/en/support/network-and-i-o/ethernet-products/000005584.html
but given it's apparently constantly changing, there's no point in having it
in the help text.

Just keep a generic pointer to http://support.intel.com. Hopefully, this one
will have a longer live. It still works, at least.

Furthermore, remove a link to "the latest Intel PRO/100 network driver for
Linux", this has no place in the mainline kernel and the latest Linux driver
it offers is from 2006, anyway.

Signed-off-by: Jiri Benc <jbenc@redhat.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>