coccinelle: Add rules to find str_plural() replacements

Add rules for finding places where str_plural() can be used. This
currently finds:
54 files changed, 62 insertions(+), 61 deletions(-)

Co-developed-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Link: https://lore.kernel.org/all/fc1b25a8-6381-47c2-831c-ab6b8201a82b@intel.com/
Signed-off-by: Kees Cook <keescook@chromium.org>