util: change coreboot to lowercase

The word 'coreboot' should always be written in lowercase, even at the
start of a sentence.

Change-Id: I0a024d82d331c0794fe087e440b4e1924129a13c
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/20030
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

util/optionlist/README

@@ -1 +1 @@
-This script creates the page https://www.coreboot.org/Coreboot_Options
+This script creates the page https://www.coreboot.org/coreboot_Options

util/optionlist/kconfig2wiki

@@ -1,7 +1,7 @@
 #!/usr/bin/env python
 #
 # kconfig2wiki - Kconfig to MediaWiki converter for
-# https://www.coreboot.org/Coreboot_Options
+# https://www.coreboot.org/coreboot_Options
 #
 # Copyright (C) 2010 coresystems GmbH
 # based on http://landley.net/kdocs/make/menuconfig2html.py