Documentation/process: Add CONFIG default value to submit-checklist

Add default value review to the submit checklist, referring to the
preference for "default n" from the previous patch added to
Documentation/kbuild/kconfig-language.txt.

Cc: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Michal Marek <mmarek@suse.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-kbuild@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Signed-off-by: NDarren Hart (VMware) <dvhart@infradead.org>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>

Documentation/process/submit-checklist.rst

@@ -37,7 +37,9 @@ and elsewhere regarding submitting Linux kernel patches.
    You should be able to justify all violations that remain in
    your patch.
 
-6) Any new or modified ``CONFIG`` options don't muck up the config menu.
+6) Any new or modified ``CONFIG`` options do not muck up the config menu and
+  default to off unless they meet the exception criteria documented in
+  ``Documentation/kbuild/kconfig-language.txt`` Menu attributes: default value.
 
 7) All new ``Kconfig`` options have help text.