scripts: coccinelle: Remove strtok_r symbol from checklist

strtok_r is part of GNU99, but default Zephyr is built with C99, so,
the GNU headers are not pulled in, even if we add "--std=gnu99" it
won't override the C99 standard.

As a workaround for build we redefine the prototype, but this causes a
coding guideline warning, so, for now disable this warning
for strtok_r.

Signed-off-by: Sachin D Kulkarni <sachin.kulkarni@nordicsemi.no>