Use www.coreboot.org over coreboot.org

<https://coreboot.org> is redirected to <https://www.coreboot.org>.

```
$ curl -I https://coreboot.org
HTTP/1.1 301 Moved Permanently
Server: nginx/1.8.1
Date: Mon, 05 Jun 2017 10:41:33 GMT
Content-Type: text/html
Content-Length: 184
Connection: keep-alive
Location: https://www.coreboot.org/

```

So use the command below to use the final location to save a redirect.

```
$ git grep -l https://coreboot.org \
| xargs sed -i 's,https://coreboot.org,https://www.coreboot.org,g'
```

Change-Id: I4176c20ef31399f0063b41e3a0029cca0c1b0ff3
Signed-off-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-on: https://review.coreboot.org/20035
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

payloads/libpayload/README

@@ -8,7 +8,7 @@ code, and provides common C library symbols such as malloc() and printf().
 
 Note: This is _not_ a standard library for use with an operating system,
 rather it's only useful for coreboot payload development!
-See https://coreboot.org for details on coreboot.
+See https://www.coreboot.org for details on coreboot.
 
 
 Installation
@@ -55,7 +55,7 @@ Website and Mailing List
 The main website is https://www.coreboot.org/Libpayload.
 
 For additional information, patches, and discussions, please join the
-coreboot mailing list at https://coreboot.org/Mailinglist, where most
+coreboot mailing list at https://www.coreboot.org/Mailinglist, where most
 libpayload developers are subscribed.