scripts/coccicheck: Update reference for the corresponding documentation

Use the current name (in a comment at the beginning of this script) for
the file which was converted to the documentation format "reStructuredText"
in August 2016.

Fixes: 4b9033a3 ("docs: sphinxify coccinelle.txt and add it to dev-tools")
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Acked-by: Julia Lawall <julia.lawall@lip6.fr>
Signed-off-by: Michal Marek <mmarek@suse.com>