Documentation: Fix dead URLs to ftp.kernel.org

As ftp.kernel.org is closed [0], this commit fixes dead URLs in
documents to use www.kernel.org instead.

[0] https://www.kernel.org/shutting-down-ftp-services.html

Signed-off-by: SeongJae Park <sj38.park@gmail.com>
Acked-by: Theodore Ts'o <tytso@mit.edu>
Acked-by: David S. Miller <davem@davemloft.net>
Reviewed-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
diff --git a/Documentation/networking/e100.txt b/Documentation/networking/e100.txt
index 42ddbd4..54810b8 100644
--- a/Documentation/networking/e100.txt
+++ b/Documentation/networking/e100.txt
@@ -130,7 +130,7 @@
   version 1.6 or later is required for this functionality.
 
   The latest release of ethtool can be found from
-  http://ftp.kernel.org/pub/software/network/ethtool/
+  https://www.kernel.org/pub/software/network/ethtool/
 
   Enabling Wake on LAN* (WoL)
   ---------------------------