Use more secure HTTPS URLs for coreboot sites

The coreboot sites support HTTPS, and requests over HTTP with SSL are
also redirected. So use the more secure URLs, which also saves a
request most of the times, as nothing needs to be redirected.

Run the command below to replace all occurences.

```
$ git grep -l -E 'http://(www.|review.|)coreboot.org'
| xargs sed -i 's,http://\(.*\)coreboot.org,https://\1coreboot.org,g'
```

Change-Id: If53f8b66f1ac72fb1a38fa392b26eade9963c369
Signed-off-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-on: https://review.coreboot.org/20034
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

util/nvramtool/coreboot_tables.h

@@ -8,7 +8,7 @@
 #include <stdint.h>
 
 /* Note: The contents of this file were borrowed from the coreboot source
- *       code which may be obtained from http://www.coreboot.org/.
+ *       code which may be obtained from https://www.coreboot.org/.
  *       Specifically, this code was obtained from LinuxBIOS version 1.1.8.
  */